Marketing in SL

HP's Eric Kintz has listed the "Top Ten Reasons Why I Still Need to be Convinced about Marketing on Second Life". He points to lag, population density, conflicts between SL and RL identities and brands, and limited potential for revenue. Avatar Prokofy Neva's comment is worth reading, as is much of the comment string debate, despite the awkward spacing issues.
There's a small clue in this post why some RL companies are finding Second Life challenging.