I know this is not a technical thread but I must correct some of your statements in case someone reads them and thinks them true:
You've seen paper wallets and stuff right? The reason these work and still retain their value is because they have the private key stored on the block chain.
No. The private key (should) never leave your wallet. The private key never appears in the blockchain. The two things that do appear in the blockchain are the public key and the hash of the public key which we call the Bitcoin address.
If somebody tried this everybody would be able to tell because they'd get some of the notes, check the blockchain and then notice that the private keys etc. are fake.
I assume what you are talking about is the following scenario: someone gives you a paper wallet and you accept it for payment. Now correcting you once again a paper wallet has the Bitcoin address displayed and the private key is hidden under a sticker. You can check the Bitcoin address on the block chain but all that proves is that address has the BTC.
It does not prove that you have the private key under the sticker that you need to actually claim the BTC into your wallet. The only way to know for sure if a paper wallet/note is legit is to destroy it, open up the sticker, take out the private key and import it into your wallet. If you are smart you also move the BTC to another Bitcoin address just in case the note has been duplicated.
Counterfeit Bitcoins are an extremely unlikely scenario right now, we've already had exchanges try to fake their trade volume and it was spotted very quickly.
It is very easy to create conterfeit paper wallets. All I have to do is produce 100 paper wallets with the same Bitcoin address on the front and then "forget" to put the private key under the sticker.