When you release an address into public, I don't think anything stops people from sharing that address to people not registered in the forum and performing any search on it. From that to Google indexing the addresses, I don't think that's a big step. If you really need anonymity, just do as it's said: one address per transaction, and if you really need your coins not to be tainted, use a mixing service.
that's the number 1 way to get tainted coins