That's an interesting difference ... with casual games we have a really short window of opportunity to execute significant change.
On ratings-focused sites like Kongregate and Newgrounds we might literally only have hours to measure, judge and react to feedback and bugs before our game slips off the new games page or the ratings-damage is too great to recover from. And that's if we're lucky enough to be given a reason why "this game sucks 1/5" heh.
On the rest of the internet we have the issue of games being distributed beyond our control, once a game goes 'wild' it gets to 100s of sites and there's really only a couple of options for pushing out updates - hot load an x megabyte swf to millions, or Mochi's LiveUpdate system which requires their ads (sometimes we're not allowed to use ads).
It has always been about two things - getting lucky, and moving fast.
Playfish tried to do a lot of games "right the first time" but weren't set up to quickly fix their mistakes and have ended up performing terribly.