These scams are not directed solely at instrument sellers, they will try anything for sale on the net! Let's get these guys back to an honest living.
The purchase scam goes like this, they want to buy your musical instrument for $2,000, but they have a debtor who owes them $7500 in the States, and they want the debtor to pay you the $7500 by check and have you wire them the difference of $5500, Western Union. Then you find out the check is bogus.
They also counterfeit US Postal Money Orders; millions of dollars of these have been found! The best way to identify a genuine postal money order, postal service officials say, is to look for the telltale watermark, which, when held up to the light, should reveal an image of Benjamin Franklin. Genuine postal money orders also have a security strip running alongside the watermark, just to the right. If held to the light, a microfiber strip will show the letters "USPS" along its length.

These internet scams are not directed solely at instrument sellers, they will try anything for sale on the net. I just reply to them with a one line email, "Thou shalt not steal". Hopefully, when they send 1,000 scam emails and get back 1,000 emails saying only "Thou shalt not steal" they will get the message.

Here is one example:
Good Day, I am Eric Wright. I saw your advert and do have a customer interested in purchasing your outfits with the picture and the price, i am ok with it and my customer will issue out the certified cashier check of $6500 out to you once you recived the check i'll want you to deduct your $3000 and send the excess funds through western union to the shipping agent that will be coming for the shippment of the outfts at your location after you most have recived payment ok, if this is ok with you i'll want you to get back to me with your name and contact address as well as your name,address,city,state,zipcod,country and phone# so the payment can be deliverd out to you ok, thanks i wait your urgent reply. Eric.

Here is another:
I AM A DEALER WHO SAW YOUR ADVERT ON THE WEB. I WISH TO MAKE FURTHER ENQURIRIES AS REGARDS YOUR .... I HOPE THAT THE ..... IS STILL IN GOOD CONDITION.

THEREFORE IF THE .... IS STILL AVAILABLE FOR SALE, KINDLY SEND ME THE FOLLOWING INFORMATION

1. YOUR NAME AND ADDRESS.
2. YOUR CONTACT TELEPHONE AND FAX NUMBER.
3. THE LAST PRICE FOR THE ....

I WILL MAKE PAYMENT FOR THE ....  WITH CASHIER CHECK. I AM READY TO MAKE THE PURCHASE AS SOON AS POSSIBLE. SO CONTACT ME URGENTLY IF THE .....  IS STILL AVAILABLE FOR SALE.

REGARDS,
Why would a dealer want your fax number? Why ask for your name and address when he already has your name? I hear he's sending this email to everyone with an instrument for sale.

Please send me any more like this!!
Alison Pryce

On the other hand, please remember that the majority of people wanting to buy musical instruments are honest. Just make sure that you don't ever have to send THEM any money.