Tor: What should I consider before running an exit relay?

An exit relay's IP address appears to websites as the source of users' traffic, so abuse reports and service blocks may reach its operator.

Short answer

An exit relay's IP address appears to websites as the source of users' traffic, so abuse reports and service blocks may reach its operator. The Tor Project advises against running an exit relay from home. Review hosting-provider policies, local legal advice where relevant, an abuse-contact process, and the Project's operator requirements before enabling exits.

Sources

Tor Project: Relay types, Tor Project: Relay requirements.