Sites such as https://www.dan.me.uk/dnsbl then help people do this.
That site in particular may "warn":
> This DNS blacklist contains ALL tor nodes (entry, transit and exit nodes) - think carefully before choosing to use this list for blocking purposes.
but anyone who doesn't understand tor simply won't understand the decision and choose ALL.
Running a relay on your own address isn't sensible because of this. Nevermind an exit node.
I think it might be a problem if I also ran a mail server from home, but almost nobody does that anymore.
I could do some shenanigans on my modem and end up with a new dynamic IP from cox, but generally within hours that new IP would be on whatever list people use to track exit node IPs and the pain would start all over again.
I still contribute to Tor via VPS rentals and such, but relays are not no-risk alternatives to exit nodes. Period.
Edit: nvm, found the answer by pricechild below.
Since I've seen this come up before in many previous discussions of Tor I think it's worth emphasizing/clarifying up front: Tor relays are not the same as Tor exit nodes. Relays do not talk to the public internet, they serve only the full encrypted internal Tor virtual network. So they won't ever send out traffic from an IP under your control to some website or general Internet system (and in turn tie that IP in any way to spam/abuse/whatever, at least not for that reason). It's not necessarily hidden that it is acting as a relay, but the relay itself will have no knowledge of the traffic it's carrying.
Plenty of people have reasonable concerns about the risks/inconveniences that might come with acting as an exit node, but on both a legal and practical level there are many more jurisdictions where merely relaying encrypted traffic between other relays isn't a problem. And it's still quite helpful, both for network speed and because purely internal Tor Hidden Services do not need any exit nodes at all.