"There ought to be a law"
Lori Drew should be shunned. She should be too embarrassed to be seen in public to the point where she changes her name and moves to a new town. But any law capable of stopping what she did would also stop lots of completely harmless behavior.
The laws she was convicted of breaking were not relevant, let alone adding new ones.
(a) Whoever transmits in interstate or foreign commerce any communication, with the intent to coerce, intimidate, harass, or cause substantial emotional distress to a person, using electronic means to support severe, repeated, and hostile behavior, shall be fined under this title or imprisoned not more than two years, or both.
This makes a whole lot of beneficial behavior on the Internet risky--I've always got a problem with intent being part of the law. Eugene Volk among others have suggested quite a few legitimate behaviors that would be at least technically violations of this law.
"But we wouldn't use it like that"
Bull. Looking again at the Lori Drew case, she was convicted of hacking activities--not because she broke into a computer, but because she did something people thought justified punishment, and that was what they could find. It would be like someone who passed out flyers at a store marked "no solicitation" being convicted of burglary because they were not using the store for a purpose the owners approve of.
Most laws have unintended consequences, (or for the more cynical, consequences that were foreseen by the authors, but not meant for the public to realize until too late). We have to allow some unpleasant things to remain legal if we are going to keep the ability to run our lives with minimal interference.