By linking your Amex card to your Twitter account, you can purchase items just by tweeting the right hashtag – #buydigitalcamera, for example. Dangerous to your wallet, sure, but the convenience is undeniable. 

In related news, MasterCard finally figured out a use for QR codes! Finally, right?  Now, by enrolling in their MasterPass program, you can go shopping in a store, scan the QR code on the item, and have it either ready for pick up or automatically shipped to your home.

Genius, right?