[Nexus S General] greenblue:
Cannot duplicate your result my crespo4g:

E/hostapd (28737): Configuration file: /data/misc/wifi/hostapd.conf
E/hostapd (28737): HT (IEEE 802.11n) in 11b mode is not allowed, disabling HT capabilites
I/hostapd (28737): rfkill: Cannot open RFKILL control device
D/Tethering( 426): sendTetherStateChangedBroadcast 1, 0, 0
D/CommandListener( 82): Setting iface cfg
D/CommandListener( 82): Trying to bring up wlan0
D/Tethering( 426): Tethering wlan0
D/Tethering( 426): InitialState.processMessage what=2
D/Tethering( 426): sendTetherStateChangedBroadcast 0, 0, 0
D/Tethering( 426): Tethered wlan0
D/Tethering( 426): sendTetherStateChangedBroadcast 0, 1, 0
D/Tethering( 426): MasterInitialState.processMessage what=1
D/TetherController( 82): Setting IP forward enable = 1
D/TetherController( 82): Starting tethering services
D/TetherController( 82): Tethering services running
D/TetherController( 82): setDnsForwarders(0 = '8.8.8.8')
D/TetherController( 82): setDnsForwarders(1 = '8.8.4.4')
D/TetherController( 82): Sending update msg to dnsmasq [update_dns:8.8.8.8:8.8.4.4]
D/Tethering( 426): chooseUpstreamType(true), preferredApn =4, got type=0
D/TetherController( 82): setDnsForwarders(0 = '66.1.61.7')
D/TetherController( 82): setDnsForwarders(1 = '68.29.1.7')
D/TetherController( 82): Sending update msg to dnsmasq [update_dns:66.1.61.7:68.29.1.7]
D/Tethering( 426): notifying tethered with iface =rmnet0
D/Tethering( 426): TetheredState.processMessage what=12
W/hostapd (28737): wlan0: Could not connect to kernel driver
E/hostapd (28737): Using interface wlan0 with hwaddr 02:1a:11:f4:a8:0d and ssid "AndroidAP"
I/dnsmasq (28738): started, version 2.51 cachesize 150
I/dnsmasq (28738): compile time options: no-IPv6 GNU-getopt no-DBus no-I18N DHCP no-scripts no-TFTP
W/dnsmasq (28738): warning: no upstream servers configured
I/dnsmasq (28738): DHCP, IP range 192.168.48.2 -- 192.168.48.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.47.2 -- 192.168.47.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.46.2 -- 192.168.46.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.45.2 -- 192.168.45.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.44.2 -- 192.168.44.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.43.2 -- 192.168.43.254, lease time 1h
I/dnsmasq (28738): DHCP, IP range 192.168.42.2 -- 192.168.42.254, lease time 1h
E/dnsmasq (28738): bad address at /etc/hosts line 2
I/dnsmasq (28738): read /etc/hosts - 25730 addresses
I/dnsmasq (28738): using nameserver 8.8.4.4#53
I/dnsmasq (28738): using nameserver 8.8.8.8#53
I/dnsmasq (28738): using nameserver 68.29.1.7#53
I/dnsmasq (28738): using nameserver 66.1.61.7#53
I/hostapd (28737): wlan0: AP-STA-CONNECTED 48:5d:60:76:b3:84
I/dnsmasq (28738): DHCPREQUEST(wlan0) 192.168.43.117 [my mac address]
I/dnsmasq (28738): DHCPACK(wlan0) 192.168.43.117 [my mac address] [my laptop name]

Dmesg:

<4>[20347.004494] dhd_aoe_hostip_clr failed code -23
<4>[20347.004967] dhd_aoe_arp_clr failed code 1
<4>[20347.313182] wl_android_wifi_off in
<6>[20347.313759] wake disabled for irq 164
<4>[20347.313983] wifi_set_power = 0
<4>[20347.314058] =========== WLAN placed in RESET ========
<4>[20347.314139] dhd_prot_ioctl : bus is down. we have nothing to do
<4>[20347.314264] wlan0: set mcast_list failed, cnt 0
<4>[20347.314334] dhd_prot_ioctl : bus is down. we have nothing to do
<4>[20347.314458] wlan0: set allmulti 0 failed
<4>[20347.314526] dhd_prot_ioctl : bus is down. we have nothing to do
<4>[20347.314649] wlan0: set promisc 0 failed

Have you tried a different kernel? Tethering is working here with Matr1x kernel and my crespo4g. I have had other two reports of tethering working with your one report of tethering not working.