Getting the IP adress details and hostname etc.. can be easy however as I say it would really be about connecting that to you. If its your home IP & the law have a warrant then your ASP account details are a request away. So if some local person that doesn't like you see's your pic or prints and can connect the dots you could have made a mistake in posting them.

Totally agree on the prints Gainesville having a digital image just saves them scanning the old paper format or actually sticking a hand on the new scanner type machines. There is ways to create some anonymity such as proxies already mentioned, anonomous service providers where everyone uses the same generic user details & also using a throw away pay as you go mobile. However these cost money and in general somebody that panicked isn't being watched by the feds for posting cannabis pictures. Basically any web users privacy is at the behest of the service provider whether that is this site owner or your ISP keep within the terms of using the service and generally they will keep your data as safe as there terms of service specifies however more governments are seeking rights over internet data such as the UK's attempts to make it legal for them to intercept or read any email through any publc ISP email system without the need for a warrant. There is always the diminishing cost of return & I imagine most local police forces get enough of a supply of information from local villians informing on each other. However that doesn't stop other agenciespull out data they want. A good supply of targets for busted grow ops are hydro shops customer mailing lists. If they could hack the user details here from the backend database they would probably use any details on that they could. Also as I said this sites data could be harvested quite easily with robots. There is probably upward of dozens of spammer robots harvesting the site alone for anything that looks lke an e-mail address.

BTW

DARPA = Internet
Tim Berners Lee = The world wide web