Back when I went to school, I used to take in a packed lunch each day. The previous evening my dad would make lunches for himself, me, my brother, and sometimes my mother (she worked part-time, and would typically work from home one or two days each week). I would take the lunch in, consume it, and take my lunchbox home. My dad would wash it that evening, along with all the plates, pans and cutlery that needed washing.
I wasn't always very good at putting my lunchbox for washing - often I would take it out of my rucksack, put it on my bedroom floor, and take it down a day or three later. This annoyed my mum, because we didn't have an infinite supply of lunchboxes and if there were two or three in my room at any one time, this reduced the number available to be used for holding people's lunches. Hence, if I brought a lunchbox down late, I would get in trouble.
I didn't like getting in trouble, and so like any sensible homo economicus I acted so as to avoid getting into trouble. That is to say, if a lunchbox had been in my room for a couple of days, it was there to stay. Gradually a pile of perhaps a dozen lunchboxes built up underneath my desk, gathering mould. I don't know how long that pile was there, but I'm fairly confident the answer is in years.
Eventually, my dad started asking me for my lunchbox when he started washing up if he didn't have it. Plus, I started juggling slightly - I would return a two-day-old box in preference to the box from that day, an return an extra box at the weekend. The pile stopped growing, it just got mouldier.
One night before the bin collection, I got up in the middle of the night, filled a black bin-bag with some of the lunchboxes and put it to be taken away. For some reason I didn't do this a second time; instead, I kept a bin-bag of six mouldy lunchboxes in the shelf portion of my loft-bed.
It came to be that some work needed to be done in the attic, and the easiest way into the attic was through a trapdoor which was about three feet above my bed. At this point I somehow managed to mention the lunchboxes, and put the bag for the dustbin-men to collect, thus putting a lid on the whole affair.
There are two lessons to be learned from this. Firstly, that there really isn't much that teenage boys will dismiss as too disgusting. Secondly, be careful when you set incentives for other people: they are liable to react in unpredictable ways which may be far worse than the problem the incentives are supposed to fix.