If he is an employee acting within the scope of his employment when he writes the code, the copyright belongs to the employer because it is a "work for hire". There is no need for a contract that states the employee surrenders his rights to the company because the employee doesn't have any rights to surrender--the employer is legally the author and it is in the employer that the initial copyright vests.

exactly -- and arguably some weekend hackathon or similar event where you arguably surrender your IP to the group.

so the "you can always license any code you wrote" isn't always at all

EDIT:

so, my "exactly" above is a wrong. I see your point about signing a contract vs not. got it. I'm sticking with my arguments about "always" ..its all I have left :)

Yeah, to be clear, I'm in favor of surrendering IP to the group for an event like this, because if you split everything up at the end it'll be worthless.

BUT! Terms like this need (both legally and ethically) to be explicit, and should have provisions for both "person X stays on-board" and "person X leaves after the weekend."

Does "work for hire" extend to verbal contracts?

No. See http://www.copyright.gov/circs/circ09.pdf . "A work created by an independent contractor can be a work made for hire only if (a) .. and (b) there is a written agreement between parties specifying that the work is a work made for hire." (Emphasis mine.)