Some surprising outdoor advertising

I wrote about Mflow last week as it launched in public beta, with a few thousand participants. It is a great concept (which I'm intending to buy some music from soon... will report back) but I was really surprised to see what looked like an ad for them at Oxford Circus - it seems to be such a spreadable product (or will be once you can bring your social graph in) that this is far too early for mass media advertising. Well, if you can't currently import your social graph then surely this is a complete waste of money? Iron out the tech stuff while it is in beta, then scale?
and on the subject of spreadable ideas relying on advertising, the same train contained this slightly desperate plea to use one of the original idea viruses... Hotmail. MSFT are actually investing in paid media that promotes.... a spam filter. How are the mighty fallen