At my company we're doing something similar. Since the scale is a bit higher (several hundred items available) we're doing credit card holds to ensure buyers aren't doing this. If anyone backs out, it makes it a logistical nightmare to work out the new winners.
Of course, it also makes it a bit tricky if you want to edit your bid, since card holds can't be modified after the fact (except for hotels/restaurants).
It looks like in this case, the scale was small enough and the buyers/seller have enough trust not to make bogus bids.
the Vickrey auction mechanism itself is incentive compatible - each agent maximizes their utility by bidding their true value. the article wasn't explicit on this front* but it's true!
* "All buyers will likely all pay less than they were willing to pay, which makes ‘em feel like they got a good deal." -- buyers maximize utility by bidding true value, if they bid true value, they will _always_ pay no more than their true value, so the expected value is positive. there's no "likely" to it!
