[Samsung Galaxy Nexus] Mevordel:
As promised, full logcat and dmesg attached. I don't know if they're worth anything, but at least they're data. The relevant section of logcat excerpted here:

I/Gecko ( 115): Attempting load of libEGL.so
D/libEGL ( 115): loaded /system/lib/egl/libGLES_android.so
D/libEGL ( 115): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so
D/libEGL ( 115): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so
D/libEGL ( 115): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so
I/HWComposer( 115): Creating new instance
E/GeckoConsole( 115): OpenGL compositor Initialized Succesfully.
E/GeckoConsole( 115): Version: OpenGL ES 2.0 build 1.8@785978
E/GeckoConsole( 115): Vendor: Imagination Technologies
E/GeckoConsole( 115): Renderer: PowerVR SGX 540
E/GeckoConsole( 115): FBO Texture Target: TEXTURE_2D
I/Gonk ( 115): Setting nice for pid 258 to 1
I/Gonk ( 115): Changed nice for pid 258 from 0 to 1.
E/IMGSRV ( 115): :0: compositionComplete: GLESFlushBuffersGCNoContext failed
E/IMGSRV ( 115): :0: compositionComplete: Foreign (probably software) GLES detected! Enabling workarounds.
...
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
E/GeckoConsole( 115): [JavaScript Error: "TypeError: callback is not a function" {file: "app://keyboard.gaiamobile.org/js/keyboard.js" line: 533}]
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
E/GeckoConsole( 258): Could not read chrome manifest 'file:///system/b2g/chrome.manifest'.
E/GeckoConsole( 238): [JavaScript Warning: "Unknown property 'user-select'. Declaration dropped." {file: "app://communications.gaiamobile.org/ftu/css/style.css" line: 9 column: 13 source: " user-select: none;"}]
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
...
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
...
E/Sandbox ( 258): install_syscall_filter() failed
...
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
...
I/Gecko ( 258): Attempting load of libEGL.so
D/libEGL ( 258): loaded /system/lib/egl/libGLES_android.so
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
D/libEGL ( 258): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so
D/libEGL ( 258): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so
D/libEGL ( 258): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so
I/Gecko ( 258): SharedSurface_Gralloc::Create -------
I/Gecko ( 258): SharedSurface_Gralloc::Create: success -- surface 0x4418b600, GraphicBuffer 0x44015f00.
I/Gecko ( 258): SharedSurface_Gralloc::Create -------
I/Gecko ( 258): SharedSurface_Gralloc::Create: success -- surface 0x44a9fc40, GraphicBuffer 0x440caa00.
...
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
E/IMGSRV ( 258): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 258): unlock(...) failed -22 (Invalid argument)
E/IMGSRV ( 115): :0: gralloc_module_unlock: Buffer is already unlocked
W/GraphicBufferMapper( 115): unlock(...) failed -22 (Invalid argument)
...

And then a bajillion of those last two lines repeated, with more spammed every time I touch the screen.

EDIT: Here's an strace of the b2g service while moving my finger around:

I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)
I//system/xbin/strace( 115): msgget(0x1, 0xbe827fe8, 0x1, 0x413fa471) = 0
I//system/xbin/strace( 115): write(27, "\0", 1) = 1
I//system/xbin/strace( 115): msgget(0x1, 0xbe828778, 0, 0x1) = 0
I//system/xbin/strace( 115): semget(0x21, 0xbe828658, 0x10, 0xffffffff) = 1
I//system/xbin/strace( 115): read(34, "w", 32) = 1
I//system/xbin/strace( 115): read(34, 0xbe828628, 32) = -1 EAGAIN (Try again)