Don't be deluded. It's not totally safe to post on the web. I worked for an ISP and when subpena's came in for information I had to by law publish what sites you went to, when, etc. An ISP knows this information even if the website you are posting on does not.

Most of the times I dealt with the law it had to do with pedophilia though. Very few 'other' things.'

Use a masking service to hide your IP. Even this is not foolproof.