many people/businesses are relying up cloud services to work - letting people to search across different services and with multiple accounts on each service would be helpful.
It's as easy as Paypal (or easier) using email to sending money. If they can figure out the secure concern (time will tell) or say it's 100 percent secure, it would be quite awesome. I agree, not sure how it prevents spoofing or email being compromised problem.
interesting to having recommendation function as part of SQL query. Not sure how much latency/delay is added executing recommendation query vs standard query against a big dataset.