Picture this scene familiar to anyone living in what passes for the civilised world. You're feeling thirsty/hungry and are wondering what to do about it when suddenly you spy a traditionally garish box, sitting there by a wall, just waiting for your custom. Fishing through your wallet, you can just scrape together the required amount of coins; you post them in and press the number for the sugar/fat-loaded item that you want. The machine gives a whirr and pushes out the little plastic coil behind your goods, but then... catastrophe: the packet is suspended and will not fall. You have no more change and are now angry as well as thirsty or hungry. You have just lost at vending machine roulette.
Is It Possible to Win?
Yes! Some machines now are equipped with a pressure pad system. In other words, you put your money in and press the button. If the chocolate falls, this registers and your cash is taken; if not, you get it back. You can then put it back in, press the same button, and more often than not you are the lucky recipient of a two for one offer.
You might also get a 'win' when you pick your change out of the metal box at the bottom. It's amazing how many people forget or maybe don't even bother to pick up their change. Checking the little box whether you have change or not when you get a coffee is perhaps one way to get a free coffee per 20 visits - checking every time you walk past the machine is perhaps best reserved for people with very little money1. Of course, equally likely is that the machine will simply refuse to give you your change, pretexting that it gave its last coppers to the person before you. Some machines warn you that no change will be given, some do not.
Is There an Equivalent of Card Counting?
Well, there are certainly safe bets. In a mixed confectionery and soft drinks machine, the cans will nearly always come out as required. Taller, thinner chocolate bars (Bounty, for example) seem to be more susceptible to getting stuck than the squatter Mars or Snickers.
That Wasn't the Hand I Wanted!
An even worse variation on not getting anything comes from coffee machines. Every now and then these malfunction, so instead of getting a nasty but drinkable cup of coffee, you get a cup of foul-tasting gack2. You then have the problem of what to do with your full cup of boiling-hot liquid. Sensible companies have plant pots near these machines to deal with this phenomenon. An alternative way of losing is when no cup is dispensed, and the machine simply pours your beverage back into its own innards.
Playing for High Stakes
If your item is stuck by what appears to be the tiniest of margins, and there is no-one around, you might just want to consider giving the machine a nudge with your shoulder. Don't kick the machine or run into it at full pelt - you will hurt yourself, as the machine is heavy. Don't bother ferreting around in the machinery; there are mechanisms to make liberating things impossible. And especially, don't tilt the machine - you don't want to end up like this Darwin award-winner, who staked his life on one can of fizzy drink - Russian vending machine roulette.
Can't I complain? I paid for that chocolate - we had a contract! Yes certainly - but - think about how much your time is worth and what the delivery mechanisms are for getting back your money. You ring the number - assuming someone picks up, you explain the problem and give the number of the machine. In the time that someone comes and gives you what you are owed, you could have written a small novella or done something far more productive. Unless you have literally nothing else to do, this is not recommended.
Vending Machine Roulette in Culture
In the film Dr Strangelove there is a classic vending machine moment where Peter Sellers tries to get change to make a call... One of the Zork games3 also has a take on this where you try various options4 to get a note out of a wheezing vending machine - help comes from an unlikely source. There is also a very funny French series of five minute shorts called Camera Café based around an office vending machine, which started on TV and have been adapted around the world. They've been going for years, so they've covered just about everything that can happen when you put your coins in - and a lot of office dynamics as well, obviously.