So in the comic book prequel to the upcoming Star Trek movie...

*spoiler warning*

the planet Romulus is destroyed.

Why doesn't Nero go into the past to prevent that from happening, instead of exacting his revenge? Even if the Vulcans were too slow in acting to save Romulus, would destroying their planet be of any help to Romulus? Perhaps his ship is not equipped with the material to do this, but he has plenty of time to acquire it, and who in the 23rd century can stop him?

If this happens in the prime timeline, what are the consequences of its homeworld's destruction on the Romulan Star Empire?

I don't really see it as a fitting end to the Romulans as a Federation threat, though the destruction of Romulus might make reunification with Vulcan more possible. First there was the shabby treatment of the Romulans in Nemesis. Now the comic book does this...

What impact will the comic book have on Star Trek Online?

Reliance on time travel + quantum mechanics = bad 'in-house' explanation of the place of the new movie in Star Trek canon.