Will online activity (of commentary websites like blogs, twitter, yahoo answers) always remain anonymous?

[Variant7]

If you sign up for one of these sites anonymously, the only thing that can really be traced to you is your IP address (and possibly MAC address - though not sure). My question is - would there ever be a future scenario, for whatever the reason may be, in which IP addresses begun to be linked to certain people's names - so that in a way, others could know what online activities you've been involved with?

Or, would this scenario be a breach of the right to privacy - and this information would always remain anonymous forever?
In other words, can ISP companies reveal the names of individuals linked with certain IP addresses? Or, is this against the privacy law?
What I meant in particular was, if a person is too opinionated in their online activities - can ISP's oust people like that?

[Kevin Fuck]

It's already not anonymous. ISPs do hand over customer based on IP address. E.g. police find man trying to cyber sex a child, they go to his ISP, ask them who used this IP at this time, they give info.