Yes, is it true. One or two years ago I saw a Bitcoin Blockexplorer and my address was linked to my account here from Bitcointalk, but I didn't do that. They just took the data here from the forum for it. Unfortunately I can't find a link to it anymore. Just by such a thing, you can break the annonimity. For most private people it is hard to link a name to an address (almost impossible, actually), but there are already companies that are specialized in such an analysis of the Bitcoin network and these data are also used to find illegal transactions. So Bitcoin is really only semi-annonymous.