Yes bitcoin mixer sites. https://en.bitcoin.it/wiki/Bitcoin_Laundry
Do these sites provide privacy in real mean?
So long as they don't keep records and doesn't give the info to anyone then yes. But most of the time you can't exactly verify if a service is keeping records or not, they'll just tell you that they don't and that's it.
But if your bitcoins aren't acquired by some illegal means then there should be no problem in using mixer just to make them impossible to trace by normal users.
Yeah. Many VPN services also say it does not log. However, when an illegal incident takes place over their systems, they share all the records with the states.
Can not we develop such a system by ourselves? We can be sure about the correctness of the system we have developed
