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PS: a modified HOSTS file will do away with most ads in Internet Explorer.  There's no need to purchase or run additional anti-ad software.

Yeah, but Internet Explorer sucks, especially when you line it up against Firefox. Can the hosts file fix be turned on and off on the fly while running IE? Can it deliver me an icon showing me there's a Flash video and clicking on it will allow it, while not clicking will not play it?
And so on and so on...

Most of us using Firefox are doing so because it's a far superior browser. Most of the graphics people I know use either Firefox or Opera, mostly Firefox it seems, and most IE users I've shown Firefox to have never gone back to IE.

As for Renderosity driving people away, I doubt it. There have been at least two mass exoduses from here in the past decade and this current event is barely enough to inspire a trickle compared to the other things. 
People who say they won't get their free stuff from here or won't buy something just because it's from here are really only spiting themselves. The people who truly do that will be such a minority as to barely make any difference to Renderosity, and it will be they who end up doing without, not the site.