MySpaceMan claims to be the "first Myspace Advertising Agency of it's kind" and says it uses its own profile to gain tons of friends and then leaves promo comments on their profile pages. The price of a thousand friends these days? $79.
Forbes recently ran a story on the undeground MySpace economy and mentioned a few ad tools that have emerged: "Another subset of sites has cashed in on MySpace's popularity by creating and selling software designed to automate tasks within the network, such as inviting and confirming friends, posting messages and sending bulletins."
Here's a MySpace page for Wendy's Square Burger done as a part of their It's Good to be Square campaign. The square burger's profile has 90,868 friends, with fans leaving notes such as this one:
i love you square.
you make me warm inside.
for your squareness
And a beautiful comment to a related post on O'Relly Radar: "What happens when adverts sign up to be friends with each other?"