Mozilla's crash stats often show Flash as a very large percentage of crashes. You can see a dozen or so crash lines in there that happen in NPSWF32 or "Flash Plugin":<p><a href="http://crash-stats.mozilla.com/query/query?product=Firefox&#38;version=Firefox%3A3.5.7&#38;date=&#38;range_value=1&#38;range_unit=weeks&#38;query_search=signature&#38;query_type=exact&#38;query=&#38;build_id=&#38;do_query=1" rel="nofollow">http://crash-stats.mozilla.com/query/query?product=Firefox&#...</a><p>I think that plugin instability is a big problem overall, probably just as big as the 32/64-bit plugin divide, which itself was a serious blocking problem on 64-bit Linux for a while.