When developers happen to be doing user support on the mailing list/forum/whatever you use, the importance of writing quality technical doc becomes more readily

When developers happen to be doing user support on the mailing list/forum/whatever you use, the importance of writing quality technical doc becomes more readily apparent to them. The volume of questions diminishes as the doc improves, they become more interesting, and you can get the simple ones out of the way by sending a link without remorse because you know it does contain exactly what the user was looking for. Of course it takes a little while for this to really engage, you'll need to kick a few people in the bottom to get past the initial investment, but in my experience it definitely works.