Found an interesting article on High Scalability blog (another must-read web site) on how PostgreSQL improves locking behavior in high-volume transaction environment.
Needless to say, the feature is
totally proprietary and not available in other database products. Improved locking behavior ⇒ improved lock-in.
Moral of the story: Stop yammering. Networking is no different from any other field of IT.
Update: Yep, I goofed up on the proprietary bit (it was one of those “I don’t think this word means what you think it means” gotchas). However, if you think open source product can't have proprietary features or you can’t get locked into an open-source product, I congratulate you on your rosy perspective. Reality smudged mine years ago.