Do we feel free to write everything we like on the Internet?

I was in a meeting last month in Spain. Mostly researchers, people from the academic world, and familiar with the Internet. We were discussing about virtual lifes and their boundaries, ethics in it, privacy and so on. You know SecondLife and things like that... like blogs for instance ;-). One guy told that when he started to use blogs he was quite unaware of some aspects of the power of the Internet and of search engines. Because that tool was virtual, he did feel like writing his own diary, knowing that just some friends of him or some "smart" people would have read it. Then search engines started to duplicate this virtual world, making a picture that eventually would last in time. This picture is there and searchable even if you delete your record, because you do not feel confortable with it any more. This was the point made by that guy: he started noting down his own considerations in the blog, signing with his real name in the unreal virtual world, and after that he decided that it was not a good idea to share that with other unknown people. But the search engines had already done their jobs: making a copy of the virtual world and associate it to his name. So anyone today can easily find this material simply searching for content associated to him.
Today most people use a nickname in their virtual lifes. But maybe they associate photos to it, or videos. In the next future searching engine will be capable of scanning those photos and videos and recognize people in it. Should we put a nickphoto of us? Or just do not trust the Internet and simply discuss about how weather is today? (quite clowdy and cold I would say....)