Twitter quietly began its “Who to follow” notes last week, offering users suggested people to follow based on a specific formula. But is it good or bad for users, and for Twitter's revenue?

Laurie Sullivan at MediaPost writes: “Who should you follow? Twitter has the answer. The company introduced ... Suggestions For You, which recommends people you should follow, and began rolling it out during the weekend as the service went down briefly for a scheduled maintenance.

”The algorithms in the feature, built by our user relevance team suggest people you don't currently follow that you may find interesting, explains a post on the company's blog. The suggestions are based people you follow and the people they follow. You'll see these suggestions on Twitter.com and the Find People section. If you like a suggestion, click 'follow'; if you don't, click 'hide,' and Twitter will try not to suggest that user again."

“What this means for third-parties doing these kind of recommendations, remains to be seen,” adds MG Siegler at TechCrunch. “Interestingly enough, the most popular of these, Mr. Tweet, is apparently undergoing a major overhaul which was due to be completed in July -- it's now August. And again, the main killer aspect of Twitter's solution is that it's on Twitter.com front and center. That will be hard to compete against.

“As an interesting side note, with the Who to follow widget now placed so prominently, Twitter has shoved the small promotional ad unit to the bottom of the right sidebar. Hopefully no one is paying for those (which, as far as I know, they aren't) because they're about to get clicked on a lot less.”

We shall see.