Deploying this heuristic to Mozilla's crash reporting infrastructure has been eye opening: if I take the 10 most common crashes on Windows, 7 are out-of-memory conditions - that is, not bugs - and 3 are likely caused by bad memory.
You've read that right, three out of the ten most common reasons why Firefox crashes on Windows are caused by memory that's gone bad. 11/17
Now there's a few things that are worth mentioning: users with bad hardware will be over-represented in this category, their machines will crash far more often than others.
The second thing is that Firefox is exceptionally stable, we've driven down its crash rate by more than >70% in the last few years. But Firefox is also a 30 million-lines-of-code monster. There are bugs in there, but they're less common than hardware failures! 12/17