If there's ever been a case for GC being fatal, it's the rise and fall of AS3. My mainstay is heavy image processing and procedural animation in Flex/Flash. While we do, finally, have a bit of control over the GC, it wasn't so until very recently and after a lot of battles. So the best you could do was to understand how the GC worked, and try to write code that would mark objects you wanted marked, and trigger the GC to run when you wanted it to run. In other words, in AS3, the only real choice was to write a management layer over the built-in buffer...

Not surprisingly, very few people employed to write Flash code actually understood anything about how memory was allocated or managed; nor did they care, because it was so easy to ignore what was going on in their little embedded applications, since much of the time the AVM2 GC let you get away with murder. Other than an endless stream of FlashKit threads where people couldn't understand how a locally scoped Tween had suddenly stopped haflway through completion, no one paid much attention. This gave rise to the phenomenon of the massive-memory-munching Flash widget, and arguably to the (as-yet-unofficial) death of Flash itself.

The problem was simply that AS3 is way too powerful and potentially dangerous of a language to put in the hands of coders who don't know or don't care about memory management; it sits there in your browser basically running Java, but with the casual auto-loading aspects of Javascript. Moreover, like Javascript, Flash GC works differently depending on environment - the projector is very clean; AIR has its own methods to call; individual browsers running Flash plugins actually specify their own ideal levels of memory usage and prevent the GC from running until those are reached, and there's nothing you can do to make a user's browser collect sooner than it wants to. (Almost nothing. We found out that opening some kinds of local connections forced GC in some cases...among other tricks). Yet the subject was consistently downplayed by Adobe and there was very little documentation on best practices to reduce the footprint of programs. Guys like Grant, Jean Phillipe and me had to work things out for ourselves as to how the GC actually functioned, and then try to educate other coders on the forums, etc.

Javascript 1.5 is another language ripe for GC problems, in which there is no hope of better tools to make the functioning of the GC less opaque, barring a sudden massive adoption of JS 2.0. The definition of "badly written" Flash code that everyone always complains about is heavy code that doesn't consistently clean up after itself. You can write a particle system in AS3 with 100k particles on screen and no major CPU impact; the trick is knowing how and when to force collection, how to (not) link events to the display chain, etc. It wouldn't be an exaggeration to say that most AS3 optimization has to do with working around the GC in some way.

The same problems are rampant in JS. The non-coding population's not as familiar with the results because it's more transparent in the browser and, by and large, the programs don't try to reach the same levels of complexity; plus when they crash, they haven't been trained to think "oh damn, Javascript crashed my browser again." However GC is a problem that all front-end developers need to make themselves extremely familiar with if they plan to write browser code that doesn't hog memory and ultimately collapse...and it's much harder to do that in a runtime browser script than it is in compiled code.