I have had my own software development company since I was basically 22. Every few years I get a full time job and let the guys know I might go feral again. So I usually get the "2 years" clause on anything I touch. A very small price to pay for being my own job reference, really.
What I'm saying is, unless you're coming in as an executive, I doubt the 2 year clause is enforceable and I doubt the companies would even try.
But if you adhere to them by coincidence (i.e. never turning down something you want to do because of them) then I suppose they are as irrelevant to you as they are to me.
