One thing I found which would be an interesting solution would be to offer software vendors the facility to remove abandonware from these sites.
I've seen this done to great effect on the "World of Spectrum" site, which archives a massive amount of ZX Spectrum games (probably Timex in the US, 8-bit computer).
The Underdogs have always been a great supporter of staying on the right side of abandonware ethics and I think that this could be a viable solution rather than ripping the whole site down.
One other thing to note about abandonware is this; with operating systems like Windows ME and 2000, it is becoming continually hard to get quite a lot of these titles working completely (with sound -- try doing some legacy games with Win2k and an SBLive), so the chances are the potential viewership of these sites are more experienced users... thus making reselling of these games economically unviable.
My downloading habits with abandonware only seem to be one or two older games for nostalgic purposes (purchased of course ;P), but I wouldnt go about collecting entire archives.
Just my blurb, flame me if you want, I have no ego.