Yeah, this seems rather nifty, but I'd want a lot more details about how the unique URL is generated, what protections there are against people trying to brute-force URLs to stumble upon money, and how the server/wallets are secured before using it for anything serious.

Definitely useful for introducing people, and the various "dropbox" and "business card" kind of scenarios that people have talked about. You can transfer money to somebody just by giving them the URL where you put their money.