I've just come back from a few days at the Edinburgh Festival. One of the things that I noticed was the sheer amount of free WiFi available, especially at the festival venues themselves, but also at a huge number of cafes, pubs & other places. Many such locations had 5+ laptop users at any time. There are far fewer major chains of cafes with commercial hotspots than there are in London.
It's just struck me that maybe a possible business model for femtocell operators could be to supply femtos to similar venue owners, to enable wider use of data connectivity for their visitors, especially if the operator is also providing the broadband connection. It ought to be possible to charge a somewhat higher price to businesses like cafes than is reasonable for average consumers at home.
That said, there would be a number of challenges - principally whether it would be possible to create an operator-neutral femto (perhaps one that didn't need SIM authentication, or one that could work with multiple operators' SIMs?).
Another way could be to have some sort of multi-femto rack or chassis, with different operator's femtos as 'blades' or modules. This type of architecture could also be used for the 80%+ of households that won't be single-operator families.
There would also need to be some sort of mechanism for policy control - perhaps in terms of volume caps, or bandwidth throttling, or maximum number of current users.
Hmmmm.... now I think through the details, it's kinda tricky. But if femtos are going to have a chance to compete vs. Wifi for casual users (especially with laptops), there will need to be some way of giving hassle-free & cost-free visitor access in specific locations.