In exchange for offensive tackle Tyler Polumbus, the Lions received an undisclosed 2012 draft pick from the Seahawks. I would imagine that the draft pick is a seventh-round selection given the nature of this trade, but right now only the Lions and Seahawks know for sure.
While this is a very minor trade in the grand scheme of things, it is exactly why the term "Mayhewing" exists. The Lions picked up Polumbus off waivers last Wednesday as nothing more than some added depth at the tackle position. The chances of Polumbus making the roster were slim to none. However, by putting in a claim for him, both the Seahawks and Texans were blocked from picking up Polumbus, allowing the Lions to flip him to Seattle for a 2012 draft pick a week later and just days before he was likely going to be released again.
For Seattle, I don't think this was a bad trade, because they obviously wanted Polumbus and wanted to make sure another team didn't block them yet again. That said, it's pretty amazing how Mayhew can turn a camp body into an extra draft pick so quickly. He did something similar with Kevin O'Connell and the Jets a year ago simply by keeping an eye on the waiver wire and picking up someone that was drawing interest from other teams. (O'Connell, by the way, was waived by the Jets today.) It's not rocket science, but rather the Lions using their bad record as a positive and staying active on the waiver wire.