Hi,
I have just almost fell victim to a very cunning a seemingly legit scam, please read carefully as it could easily happen to you.
I found an ideal bike on gumtree, a 'Dolan Stryke' complete with Sram red, brand new for just £900, seemed like a bargain and also borderline too good to be true. I instantly contacted the seller and arranged to purchase it, he/she described that they would prefer not to use online payment methods such as Paypal and introduced me to a new method of payment called 'Paysafe card' ( http://www.paysafecard.com/uk/uk-paysafecard/ ) I read all about it on the website and decided I was happy to use this service, he/she stated that in order to make the payment I would buy a paysafe ticket from a local store, and I would be given a unique code, I would then send the code to a 'confirmation' email address, and paysafe would inform the seller that I have purchased the card. Then the seller would dispatch the item, and I will receive it and check it, then I can send the pin to the seller and he/she will receive payment. Initially it seemed legit, but when I saw the exact same bike and description on ebay for £2,000, I began to smell a rat.
After a bit of detective work, I found out that the 'confirmation' email was actually a third party address (ending in @safely-paysafecard.com), so if I had have emailed the unique pin containing £900 of my hard earned cash to this fake confirmation email, it would have gone directly to the seller, then he/she would instantly have access to my money with the only traceable element being an email address, so the money is as good as gone forever.
I have reported the gumtree ad and asked them to take it further, if that fails to happen I will take the liberty to do it myself.
The old internet saying of 'If its too good to be true, it probably is' springs to mind.
Sorry to ramble on a bit, but it could save you a lot of money, I was inches away from losing almost a grand...

gumtree is a thieve's paradise, there's absolutely no attempt at verification, and even when advised of stolen items they do not pull them from the site or help you trace the thief (my bike was stolen and fenced on gumtree, with a bunch of others by the same seller, a week later they still had ads from the same seller, they just don't care)

if i had my way i'd shut them down

never buy via gumtree

This alone should have been enough to convince you that it was a scam.