According to Marc Whitten, manager of Xbox Live, Microsoft will begin pulling under performing games from the service.
XBLA titles that have been out for more than six months, have a Metacritic score of less than 65%, and have a conversion rate of less than 6% will be eligible for de-listing. In other words, the wheat will be seperated from the chaff, and those titles that you can't imagine anyone would ever want will soon be gone.
Another piece of news: There is no Spring update coming.
Next Generation: EXCLUSIVE INTERVIEW: MS to Delist XBLA Titles