Among all kinds of SEO spam, unlike other types of spam, good link spam carries with it a wealth of benefits for the site being spammed:
1. It brings users. When a new social site debuts, especially when it is a "me-too" site like Quamut, getting users is tough. Unless you offer some special incentive, or your site provides something necessary that other sites don't, you have to fight a tough battle for users. If someone wants to add link spam to your site, they need to sign up. The thousands of SEO Spammers out there can quickly become thousands of new members of your site. And when the spammers sign up under multiple accounts, they can quickly become tens of thousands of new members.
2. It adds content. It might not be the best content ever written, but SEO spammers do know how to write content that, at the very least, is unique, keyword-rich and geared to any user that might stumble upon it. Contrary to popular belief, SEO spammers are not interested just in backlinks, but also in filling up the SERPs. If they can get a page on your site to rank by combining their content with strength of your site, and then convincing the user to shift to their site, the bottom line stays the same.
3. It raises stature. When your brand spanking new social network has 10,000 members and 50,000 UGC articles after only one month, your site starts to get noticed--even if most of those members are spammers and that content is primarily spam. There's a reason companies like MySpace and YouTube didn't crack down on spammers--and even explicitly allowed spam in their original Terms of Service. If you want to grow--and grow fast--no one will help as much as spammers.