It's amazing how certain scams that would never make sense in any other context, somehow become effective when associated with Bitcoins. I mean, seriously, requesting $5 from strangers over the Internet, how can it not be a scam? Who would do that in real life, as opposed to just asking friends/family/coworkers for a spot loan?
Uhh there's a big difference here that you're missing.
He wanted to make a purchase, most likely off silk road. It was Wednesday night. If he ordered from domestic vendor it's likely it would arrive in time for the weekend. If he had borrowed 5$ from a friend, the banks would have to be open. Then he'd have to go deposit into bitinstant (do they accept amounts that low?) then get the coin, wouldn't happen until Thursday 10-11am. Then place order, might not get shipped til Friday, won't arrive until next week.
Not saying anything of his creditworthiness here, but the idea itself does have merit.
When buying stuff on silkroad, if you're .5 btc short on a decent sized order *most* vendors will give you a gift code for the amount so you can place your order.
First, report him at the Scammer Accusations subforums. 
