In 20 words or less, the difference between top-down and bottom-up SOA

I've been contributing to the FastForward blogging conversation on Enterprise 2.0, where I compared the the SOA-Web 2.0 conversation to that ongoing "I'm a Mac-I'm a PC" conversation between the two dudes in those funny Apple commercials. 

Perhaps it's a fitting analogy for what we’re seeing in the SOA and Web 2.0 worlds. The “SOA” guy is the one in a corporate suit, a bit uptight, and prone to making things more complicated than they should be. The “Web 2.0″ guy, on the other hand, is the cool, good-looking one. 

Andrew Roberts picked up on the post, and also made what I think is the most concise, to-the-point comparison I've seen on the two differing approaches to starting SOA, or any type of IT project for that matter:

• The top-down, let's-spend-$20-billion type approach; and
• The bottom-up, let-a-thousand-wikis-bloom approach.

So, if you're ever on an elevator and a colleague turns to you and asks what the difference is between top-down or bottom-up SOA (happens every day), you're ready.