I think most stalking statutes would consider it a form of "following" or part of the "course of conduct" that would make a person fearful. Stalking statues vary widely from one jurisdiction to another. Some states have specific cyberstalking or other "computer crime" statutes that might make it illegal.
So the answer, as with most legal questions, is, "It depends."
We lawyers are incredibly helpful, eh?
Seriously, though, if you want to know what's legal in your own state, you'd have to read your state statutes (and maybe relevant case law). Or consult a lawyer who practices in your jurisdiction (but expect to pay for it).