It is inevitable that a system like MyBlogLog, if popular, would get spammed. I suspect it will be difficult to prevent. Spammers have quite a financial incentive to manipulate this feature since, if successful, they essentially get an advertisement for free in a placement that would normally cost thousands.
Note that the spam attempts only started once Yahoo acquired MyBlogLog. Before this point, MyBlogLog was not big enough to attract spammers attention. With the Yahoo acquisition, a financial incentive appeared.
All very predictable. In my October 2005 post, "Getting the crap out of user-generated content", I said:
Small sites work dandy when they're only used by early adopters. Early adopters are dedicated, so the quality of the content is high. Traffic is low, so spammers don't care about them.See also my earlier posts, "Growth, crap, and spam" and "Digg struggles with spam".
As they grow, as traffic increases and the products start to attract a mainstream audience, the incentive for spam go up. Suddenly, there's a profit motive, an ability to reach a wide audience at low cost. The spam floods in.
Websites hosting user-generated content need to be designed with the idea that much of the content will be crap or spam.