Figured you guys would like to know...
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According to Whitten, 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 desliting. Microsoft will give three months of notice before these titles are removed.
Other interesting tidbits:
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So we are officially increasing our XBLA game size limits dramatically from 150mb to 350mb.
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In addition to allowing these bigger and better games we will be delisting older underperforming titles in order to keep the service focused on a section of high quality games. Finally, we are also going to be putting our money where our mouth is here and are launching a new fully funded 1st party studio which will be focused on high quality digital content creation.
From next-gen.biz.