The best solution for this type of spam is a denial of time attack. To do so, you engage the offender in repeated, mundane questions about the product in question. They have to be questions of a nature that will require some time to respond though. This will tie up the spammer, thinking that they have set a hook and might make a sale, lol.

An example would be "how does this work for the alpha stock market" or something of that nature.

I use a 'throw away' email account, set up on hotmail for this purpose.

Another thing that can be done is repeatedly visiting all the sites that ad link to the spammer. Generally, they pay per hit, so it will cost them out of pocket for ad hits.