The fact they both left shortly after a year would perhaps point to something a bit more substantial than a signing bonus. More like a retention bonus tied to the acquisition. That's what I thought when I read about LC's departure the other day anyway.
I'm always slightly skeptical ;) but these things just seem like a way to avoid having your baby in the dead pool to me.
[1] http://www.sixapart.com/blog/2008/12/welcome-pownce-team.htm... [2] http://www.washingtonpost.com/wp-dyn/content/article/2010/02...