A bit old, but a good post by Ed Sim at BeyondVC:
I recently helped negotiate an employment contract for a new hire at a portfolio company. It was clear from the very beginning that this new VP of Marketing was the right fit for the company and that the chemistry was there. Both sides were excited about moving forward until we got to the employment contract. In theory, we were in general agreement on salary range, bonus, etc. but what ended up scaring us was the fact that every issue, big or small, was negotiated to the nth degree. There was no give from the other side and when issues such as vacation days were hotly contested, I got quite concerned. (full post)
A side note to this on corporate partnerships is not to beat down the other side. Some people get caught up in the negotiating game and want to take and take if they gain leverage or see the opportunity. It's not a competition and egos should be checked at the door.
If you make a very one-sided deal, it can lead to a very unhappy partner down the road that can lead to other problems especially if the tables turn. If you really want a solid long-term partner, get the most you can to benefit your company but remember not to take the person's underwear.