I dunno what to thinks about this services.. do they make money laundering easier

Mixing coins is It is something completely different than money laundering.. But i was always wonderend if for any "secret agencies" it is not a perfect idea to open mixing service just to know who is trying to hide transactions or some large amounts of Bitcoin..

They are the same if thats your intent. Money laundering involves transferring money through foreign banks in order to hide the source or origins. If you mix the coins, then you are essentially doing the same thing. However it is even harder for the banks to figure out you had the bitcoins in the first place.
There is still a slight difference between the money laundering and coin mixing. Money laundering is not so much about hiding money as making it appear legal. You hide the origin of the money to use it publicly as a law-abiding citizen. When you mix your coins, you typically don't want to hide their origin because in most cases it is already well hidden by the Bitcoin network itself. You just want to break the link between the money and yourself (your wallet), so that these coins are no longer recognized as yours unlike money laundering. That seems to be the main difference.