Please cite.

Folk are up-voting you, so the consensus is in your favour, but let's please out the facts, not hearsay.

Really? I always hear that non-competes are generally not upheld.

You hear wrong (e.g. http://en.wikipedia.org/wiki/Non-compete_clause):

"Most jurisdictions in which such contracts have been examined by the courts have deemed CNCs to be legally binding so long as the clause contains reasonable limitations as to the geographical area and time period in which an employee of a company may not compete. "

California tends to be the most employee-friendly wrt non-competes, but even here you can construct one that is valid, for certain classes of employees and with many restrictions.