It might be against the terms of service of the website you're crawling, which puts you in violation of the Computer Fraud and Abuse Act (i.e. you're considered to be "hacking" them).
Well however you classify it doesn't matter, what matters is how the government classifies it. There's the tragic story of Aaron Swartz who was caught up in this non-sense: https://en.wikipedia.org/wiki/Aaron_Swartz.
1) It's illegal to impersonate law enforcement online.
2) It's illegal to commit fraud by pretending to be someone else online (when, for example, using someone else's credit card or opening a bank account in their name).
3) You can be sued for things that are totally legal, such as blemishing Google's brand my impersonate them and doing things that annoy people.