Upkeep and domains cost assuming you are opening it to other users, if it gets popular you have to scale up your operation which costs more.

Here's a fun one... If you are hosting content that could get a DMCA from companies in the US, then you need to make sure you have filed a DMCA Agent with the US Government that handles those claims, section 512 also requires the termination of repeat infringers. In order to qualify for the safe harbor you must have a registered agent.

If you are running it on a home server, read the ToS from your ISP, some do not allow that on home internet service. My ISP has a clause that says my service is for my household use only and that I can't open it for any sort of "high-volume purpose."

I'm just spitballing here, it'd probably just be a fun thing for you though, just be aware of that DMCA thing if it catches on though. I have no clue if other countries have similar requirements.

it won't be automatically defederated, but you won't have a cache built up, meaning that some older posts in communities you visit, as well as older comments won't show up at first.

Though, unless you also want to implement a ruleset and moderate the instance (in addition to doing legal stuff), I would advise keeping it closed to yourself.

The main problems are the headaches you get while setting it up. Kbin is not in a state where you can just run a script and it works.

I'm pondering whether to embark on that journey myself, as I have a topic that I feel deserves it's own instance. I have some experience in setting up websites (going back to forums days with phpBB, vBulletin, and Invision going through WordPress and Pligg) but those were relatively easy as there were installers and plenty of info online. kbin will be a challenge for sure but also an exciting project I feel.

After the kerfuffle recently about one of the NSFW instances allowing drawn CSAM, I reckon you could get in trouble if you federate with an instance like that if you're hosting in a jurisdiction where that sort of content is illegal. Or imagine in the future, deepfake celebrity porn may get federated onto your instance and put you in the firing line for hosting that illegal content. NSFW is the most obvious, but I think there could be ramifications for hosting content on your own instance federate din from elsewhere that is illegal in your jurisdiction.

Thank you. I was curious about this too and casually interested, but now realize I don't want the liabilities for DMCA, NSFW that people have mentioned.