This behaviour makes Firefox prone to accidental zoom. Safari and Chrome both have a threshold (i.e you have to move through the gesture a little ways) before the behaviour starts happening.

FWIW I haven't ever accidentally triggered zooming on my mac. There is a bit of a gesture you need to get through before it engages and it feels fine to me.

On touchscreens, where we do our own gesture detection, we have a threshold that needs to be passed.

On Mac touchpads, however, I think the gesture detection is done in the OS, so I'm not sure what degree of control we have over it.

In my testing it seems like Safari and Firefox have about the same amount of "delay" before reacting to a pinch, and Chrome has a larger "delay" then Safari and Firefox.

Indeed. I also see a similar delay in Firefox and Safari. It seemed like less when I reported this. That being said I seem to trigger accidental zoom a fair amount in Firefox (once a day?)

@jeff: do you still feel this is the case?

It hasn't bothered me lately.