According to Wikipedia, and is implied in the show, Sylar cannot obtain abilities from the dead, even if the brain is intact. In this chapter we see how Sylar became telekinetic, by bashing Brian Davis' head with a chunk of quatz. While that may not have killed him I doubt his brain was undamaged. It may be mentioned in the graphic novels but I am curious if somebody had died while he was trying to obtain their abilities, negating that possibility.

On the main Heroes page I asked about the webisodes, if they were any good. Well I watched them and I'd say only The Recruit series was decent, hopefully that actress returns.