Some say yes and others aren’t so sure. There is a technique that can be used where the seo company will build a link wheel using several (or more) web 2.0 websites. These mini sites are then social book marked and the rss feeds are then submitted to aggregators to be published around the web. This can provide a supply of back links to your site as well as showing your authority, because after all, you have lots of sites pointing at you shouting “hey! This guy knows what he is talking about!”
All im going to say is “be cautious” as if a sudden increase in web 2.0 sites popping up and pointing to your site shouts “SPAM!”
Google are aware that this method is in use and know the tell tail signs of a would be spammer so if you do decide to look into link wheels, just remember that if the referring site (or sites) are earmarked as spam, you could potentially incur a penalty, or at the very least loose your PR authority resulting in a possible drop in positions in the search engines.