Combine that with the positive 'word of mouth' I've encountered so far from non-technical types and it's possible we haven't seen the knee of the curve yet in adoption growth.
... (Hmm, before making that assertion I'd better test it, test test test)...
Well, perhaps I should amend that to "up until very recently, Chrome was visibly faster". As it happens I just went from Firefox 3.5 to 3.6 on this machine yesterday, and a deliberately-subjective performance test I just ran has Chrome and Firefox a lot closer to indistinguishable difference. (As an end user, I don't care about 10% differences on this or that benchmark.) I had been using Chrome for the last two weeks, but I have very badly missed NoScript and right click -> "Block images from this server". (Stupid flabby stomach ads.) Now I think I'm headed back.
But I suppose I can salvage my thesis by saying that at least until recently Chrome had a significant advantage over Firefox. If Firefox's performance catches up, that may staunch the bleeding, because if Chrome isn't much faster, why switch? Firefox definitely has more features, and nobody really cares about HTML5 right now; by the time they do FF will be there.
Right, and why would anything else matter for a web browser?
At least I'm sure that Google Chrome's increase in market share doesn't necessitate a reduction for FF (though some reduction is almost certain).