All true, but I'm still dubious about the retail potential here and would love to be proved wrong. As another poster pointed out, staying in a hotel does not provide a closed eco-system of wi-fi use, as business travelers would also need to be protected in convention centers, restaurants, transit hubs, what have you.

I think a target rich environment would be corporate headquarters buildings. When I'm in a bank headquarters, for example, they usually have a dual wi-fi system, one for employees and one for guests. There are no other options for accessing the internet and people are there pretty much all day and financial considerations are at stake. Ditto for law firms, Blank Rome, for one, at least in their NYC headquarters.