Is it possible to search the block chain by amount of bitcoin?

[wr1000]

If I do a shared send on blockchain.info, the bitcoins I send are mixed and a snooper shouldn't be able to link the sending and receiving addresses together. However, would it be possible for an adversary to search the block chain by amount of bitcoin sent? Eventually the correct number of bitcoins must be sent to the receiving address. Since an amount is probably pretty unique, it seems easy to link two addresses together by matching amounts.