why are proxies required for gsa?

i dont get whyyou need them if its subbing to different sites each time?

The same reason you need them when submitting automated blog comments in Scrapebox. Your home IP is going to end up on the StopForumSpam database if you don't use them, not to mention it's much easier for people to report you to your ISP if they don't like what you're doing.

Different sites (i.e. forums) + centralized database of blacklisted IP's = proxies necessary

i think its not necessary for this so long as you have a bulletproof host who doesnt mind the complaints since i used to run xrumer without and ye i got banned a cpl times but it would take a few weeks and we are talking milions of links there. i doubt a puny cpl of thousand that gsa makes will be heavy enough to make a dent