In California, when you (A) Hire a realtor and (B) List your home, the seller determines both the sellers and buyers commission, and it's 100% negotiated (well, the sellers commission is. You just chose the buyers commission). Not sure where the myth of "6%" (not 7%) commission came from. I paid my realtor a 2% base fee + a 5% kicker on anything above a base amount for selling my condo, and a flat 2% to the buyers agent. Took her six weeks of open houses to sell my place, and overseeing the renovations, and she cleared a net 2.3% on the final price. (this was in 2006) - She was with a top tier realty agency as well, Caldwell.
Can't comment on other locations, might be different.
I've heard from several homesellers who were quite convinced either you couldn't negotiate down (or that you wouldn't want to), unless you were doing repeat business. There may be some more flexibility now because I think people are getting increasingly frustrated and looking to alternatives.
Can't comment on other locations, might be different.