I ran a few exits for about about ~5 years. In those 5 years, my hosting provider (DigitalOcean) received 3 subpoenas for my account information.
The first two were random. The 1st one was someone sent a bomb threat email to a university. The 2nd one was someone sending a phishing email.
The last and final subpoena was the most serious one. Some nation-state hackers from Qatar had ended up using my exit IP to break into some email accounts belonging to people they were interested in and spied upon them and stole some info.
Thankfully both the Tor Project and the EFF were able to help me pro-bono. The EFF lawyer that was assigned to me helped me fight this subpoena but ultimately we had to turn over my account information to the DOJ + I had to give an affidavit stating that I was simply just an operator and nothing on the server in question would be useful to their investigation (by design).
The stress of having to deal with law enforcement, lawyers, and having to entertain the possibility of having my home raided over something so silly ultimately led to me finally shutting down my exits.
Even though I had all of my exits using a reduced exit policy and I would blacklist known malicious IPs and c2/malware infra from being able to use it, I was still a target.
I feel law enforcement realizes this is a big weakness they can target since a lot of Tor exit operators are individuals with not a lot of resources to fight them. They can use the legal system to scare operators into shutting down.
I one day hope to resume running exits as I find it rewarding to be able to help people from around the world in a small way.