Wyrmio and mrcross both make sound technical points. However, I worked in the research department of an oil company in the early 1980s, when Dick Stratton was doing a fine--and technically sound--job in demonstrating that, subject to sensible limitations, there was no problem in running mogas in certain glider-towing types.
On a pragmatic level, I have--let's say--a friend who has been running his A-65 on mogas since 1981. This is in a high-winged type, not unlike QDMQDMQDM's usual mount. My friend has not encountered a single problem with this fuel. Indeed, when he changed to mogas, he suffered much less lead fouling with the aviation plugs he used to run. (Avgas left little lead balls behind the electrodes!)
Now I am not suggesting people go out and blindly copy my friend's approach. Not everybody enjoys gravity-feed from high wings (getting around the vapour lock problem). However, avgas has too much lead for engines like the A-65, and aerodrome fuel storage/throughput can, I suspect, be poor enough to allow more water into the fuel than happens at busy--and well-run--garage forecourts.
Now the price differential has been eroded by changes in fuel duty, there is less pressure to substitute on fuel for the other. However, it is not easy for strip flyers pick up a regular supply of avgas. On the technical side, I would suggest that it is horses for courses: the most expensive and highly-regulated answer is not always the right one!