Here's my theory on the tagline "save the cheerleader, save the world"

How has Sylar been killing these other heroes?
What caused Claire to die, even for a moment?
If you really think about it, the answer is in those questions

Sylar must need Claire's ability to regenerate. Since he only has a list of names and doesn't know everyones ability he must kill them all the same way to avoid them from regenerating.

That makes sense. Another possibility is that the writers are just making things up as they go along. Maybe the whole save the cheerleader thing is just a tagline that sounds good but isn't actually real. That's why they didn't explain the connection to saving the world in this episode, it's because there is no connection. Hope I'm wrong and they actually have a plot.

so all the heroes have regenerative powers??

why does everyone think that they will save the world soon?

hiro looked as though he was from far in the future... they could have years/seasons to save it.

I think what mandy's saying is that Sylar is on a mission to kill all the heroes - not necessarily absorb their powers. Since Sylar knew that at least one of the heroes could regenerate, and the only way to permanantly kill that hero would be to remove the brain from the body, but didn't know which one, he is killing all the heroes that way just to make sure.

That being said, I don't think that this theory holds water.

1. Sylar didn't necessarily know what powers, or the extents or limitations of said powers, there were. Chandra only made a few vague preditions, such as flight and tissue regeneration, and Slyar is working off of Chandra's research. A logical assumption is that when someone is dead, their powers stop working. We happen to know that in Claire's case, that's not true.

2. If the power absorbtion theory is correct, then a lot of things make a lot more sense. Imagine FutureHiro came from a timeline where Sylar had tissue regeneration, and was nearly invincible. Hiro discovers where this regeneration ability comes from, and figures out how to go to the past to stop it from happening in the first place - trying to find the place to insert himself that will least like cause a rift (I think he learns something important in his "do-over" with Charlie).

Shades of Terminator, huh?

I am new, hello people.

My thought is that CLAIRE may have healing capabilities beyond her own, so if NY goes Nuclear, she may be able to save ALL those affected, which is why she has to be kept alive. Because Hiro from the future came from a future apparently where Claire was dead, and he must have known that saving Claire was a huge deal for everyone, not just the heroes.

Just a thought.

Or, the cheese has simply fallen off of his cracker for whatever reason... and he's simply killing other metahumans because that is what crazy people so (see Hannibal Lector for more on this).

I don't think that is the case. The writers aren't making Sylar out to be Ted Bundy...It's a TV show. I understand what you are saying about the trophy & sociopath deal but I don't think that is his motive. I believe there will be more questions answered next week during the flashbacks. As for now we only have speculations and my speculation is that Sylar is taking peoples brains because that's the only way to eliminate Claire. And just to make sure that it is done correctly he is doing it to all the heroes to prevent them from coming back. I'm not saying they all have the ability but I am saying it's for precaution, on Sylars behalf.

I don't know how this started but I think we know enough now to determine that Sylar isn't stealing other peoples' powers. He doesn't eat their brains or anything like that.

Sylar is a sociopath that is killing heroes because he believes he must. We won't know the true motive until the flashback episode next week. Serial killers usually take something of the victom as a "trophy". Apparently in Sylar's case it's the brain. It's probably a symbol of where the power resides in the body.

But then again I'm no shrink so maybe you're right..

I like the trophy idea, kinda like Predator!