Some qualifications to terdon's answer about public IPs.
A public IP for most people these days is actually the IP of their router, not a computer. That may go on to give people access to other stuff on your computer and network but it's a layer of resistance. Most routers won't let people through by default so you're relying on the straight security of that.
Additionally, many people's public IPs rotate around between customers at their ISP. This is exactly to prevent this sort of targeted attack. A customer might rotate around hundreds of thousands of IPs, or more.
In short, direct attacks for an IP address you posted probably aren't going to be any more a problem than the waves of automated scans hackers already do.
But an IP address isn't just a number. You can
whois an IP to learn who owns it. Depending on the sort of network this provides:
- Country (usually correct)
- ISP or network owner
- Location of the network owner. Only a problem if you're in the same building (eg it's your corporate network, or a hotel or something)
You can also get a very approximate location via advertising networks.
You might be able to use this sort of information with the context it was posted, past posts, links to other profiles, random Wayback-logged content saying where you went to school. Deep digging information like this can be dangerous, but how much of that is really relevant to the IP address you posted when you posted it?
I guess that really depends who's after you.