I can't see these ever taking off either. But then again I think that the Brits are bias.
These kind of 'vanity' numbers are/were much bigger in the states:
Adverts all the time for call 1-800-lawyer and similar.
Whereas in the UK we've never really had adverts giving out a number in that way. In fact I always thought what a waste to have letters on traditional home phones - and what's the point? Of course now with sms messaging those letters are useful, but for vanity .mobis - I just don't think it will take off. Not in Britain - would have to change a culture...
But it's only a little island compared to the US