The online barter systems seem to be de facto creating an alternate currency. IIRC, the one profiled in the article uses "points" that are the equivalent of Euros (scanning, I can't verify this atm, but I read more than one article before submitting this one, so maybe I read it elsewhere). So if you have 600 points in your online account, you have the equivalent of 600 Euros to work with.
I think it isn't Greece's monetary policy that is out of whack. I haven't really studied it, but my impression from casual reading is that the economy is being crushed by things like high benefits packages for government workers. So when you engage in barter, you side step that. You trade THIS thing for THAT and there is no cost tacked on for putting money into a retirement account or paying for disability insurance etc. You just need tires and need food or you have meat and need tires, and you make the trade to meet your needs in the here and now and let tomorrow worry about itself, thus you don't reduce the value in the here and now of what you traded by setting aside one of your four tires "in case something happens" and driving on three good tires and one bad or whatever. (Trying to come up with a goods based equivalent of the overhead of retirement and so on benefits.)
Anyway, I thought it was neat that a) barter is being facilitated in part by online services b) those services are engaging in some of the same practices PayPal engages in to make sure it is secure and c) it is de facto creating a virtual currency without any intent to create currency. In fact, the intent is to side step the need for currency. Nonetheless, the tracking of points that you can spend is the essence of a currency. The single biggest real value money has is it lubricates trade by creating something universally accepted so you don't have to ask dozens of people if they will take Thing You Have in exchange for Thing You Need. You can just sell it to Person Who Needs It and then turn around and buy what you need.