Noncompete clauses

Brent Ozar wrote a great article entitled "Top 10 Questions to Ask When Taking an IT Job", which brought up something I'll definitely need to remember...that pesky noncompete clause that keeps popping up.  I have no problem with nondisclosure, with conforming to the ethical standards of only accepting freelance work that in no way competes with my main employer, etc.  However, I like the flexibility to pick up work on the side so this will be a good question to keep in mind.