In power trading there is an entire subset OTC market for delivery called FTR, or Financial Transmission Rights. Tower Research Capital thought they'd dabble in it for shits and giggles, and lost like $80M in one trade which bankrupted the shell company LLC Tower was using.
Same same with crude - the most fungible and traded storage is actually in transit on the oceans, supertankers of course. OTC traders are swapping the storage rights well before they are even off-loaded. Think about it, you have a futures contract whose front month is on the board maybe three weeks, and tanker transit is several days or more each way. Some great basis plays. There are even composite indices on tanker rates available at your favorite OTC broker. Platts is pretty much the standard for daily publications, you can also find some of them on the Bloomberg terminal in the OTC energy section.
Never doubt the appetite for trading - for God's sake, they trade Bat Guano OTC (seriously). You should see all the plastics that LME clears OTC in the physical ring.