Dan Gillmor's new column — it's hard to pick a quote from this, the whole thing's just so right on.
1) Make it all work on top of existing networks. Designers deliberately didn't try to build a single, new über-data network — it was about "networks, not a network," Bradner observes. This meant supporting multiple network types by putting a simple set of rules, now called the Internet protocols, on top. This added layer was wide open for innovation, not controlled by a few players.