[Spittie]

While bitcoin can be anonymous (buy with cash, use a mixing service, change your bitcoin address every time, only pay over tor/i2p), they aren't made for that. Also keep in mind that every transaction is public, even if it can't be traced back to you.

See https://en.bitcoin.it/wiki/Anonymity for more informations

[sliverstorm]

Not only is every transaction public, but the record of that transaction will stay around forever. Or, at least as long as Bitcoin exists, that is.