When expanded, you can see the comments that have been written or contribute your own.

Google says that it uses multiple signals based on the quality of the entry, what they know about the author, and other usercontributed signals like voting and flagging. They say they want to only keep the most relevant entries appearing in the sidebar. Sullivan says Google gave him a few other factors Use of sophisticated language Users reputation Users historyGoogle recommends commenters contribute expert insight, helpful tips, background information, and added perspective.Your Google Profile evidently plays a direct role in whether or not your comments appear. Google ranks profiles in a PageRanklike manor, so the higher you profile is ranked, the more likely your comments are able to appear. Unfortunately, you have no way of knowing your ProfileRank, says Sullivan.Ive discussed numerous times in the past about how Google is becoming one giant social network of sorts, and this seems to indicate that it is on some levels even an exclusive social network. Anyone can participate, but it sounds like you have to be somebody to get in.