http://I have had a similar experience with Jakers.  I am still a bit hesitant to call him a scammer, as from what I have read he takes an insanely long time to complete a transaction.

Jakers offered to buy from me a $25 dollar Best Buy gift card for half price (My initial forum post https://bitcointalk.org/index.php?topic=138722.msg1477557#msg1477557).  I got the card for free awhile back, and had not used in since.  I also have no rep to speak of, so trading, even at a loss, to get a decent reputation seemed like a good idea.

Here is the PM from Jakers making the request, and his reply to me saying sure (crossed this out as it was a bit hard to read it was conditional to me not having any other offers in the next 24 hours I said I would trade with him if I had no other offers within 24 hours)
http://i.imgur.com/f3Ljz8L.png




Here is the initial value of the card:
http://i.imgur.com/UM4qOs1.png




value obtained from Best Buy's gift card balance checker here: https://www-ssl.bestbuy.com/site/olstemplatemapper.jsp?id=pcat17043&type=page
A simple search of "Check giftcard balance" on the Best Buy site will take you to the same page.
After some time, I get this message: http://i.imgur.com/4Xt8M9g.png



I forget the exact context of it, as I wasn't saving all of my sent PMs.  But notice the time stamp, and lack of funds in this address: 1FyT3UQNRN9Ah1Bnp55LjoCNkDYqVzVfMH.

first four numbers blocked out for security stuff, and to keep myself from being accused of giving out the gift card number.
The PM's I have on record of me sending to Jakers:
http://i.imgur.com/3Mzubee.png?1


Here is the balance of the gift card now:
http://i.imgur.com/mbLyuHi.png


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I am still hoping to get a payment from him, but thought I should share the experience I had with this user.

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As per BCB's suggestion.  
Amount owed: 50% of $25, or about 0.7BTC to about 0.74BTC (depending on exchange rates).
Link to blockchain address for transaction: http://blockchain.info/address/1FyT3UQNRN9Ah1Bnp55LjoCNkDYqVzVfMH
Proof of promised amount: http://i.imgur.com/f3Ljz8L.png

EDIT: Made image viewable, downside is it is a bit hard to tell where text begins and ends.