When I worked for a CS department long ago, I took all the Sun Type 4 keyboards home in batches of 6 to run through my dishwasher.
I would never do it to a board unless I was really sure it was completely unpowered when disconnected, and waited days for it to dry.
There are lots of other caveats depending on the exact keyboard and exact dishwasher model.
Probably good for cooking crab legs, but would likely warp the plastic on a typical keyboard.
And about a decade ago I had a crab dinner served at a friend's house. The guy knew how to cook -- easily the best crab legs I've had (helped by the fact that he knew where to get good product). After we finished the meal, he explained that he cooked them in the dishwasher. I think part of me was grossed out, but it lasted only a few seconds ... they were extraordinary.
[0] I am, but I probably shouldn't be.
My method for cleaning my Omnikey was to fill the kitchen sink with water and clean it like one cleans a dish. After a quick towel-dry, I'd toss it in the oven for 12-or-so hours at the lowest temperature (I think about 150-200 degrees American). I did this at least 10 times during the decade and a half that I used this board (and it was sold in perfect, working condition).
I'm sure I did some damage, somewhere. There's got to be parts in that keyboard that corrode, but it always came out "like new". I haven't owned a keyboard like it since and I expect the one I use day-to-day wouldn't survive a strong gust of wind. I'm not completely, nuts, though. The first time I performed this all-day, insane, cleaning routine was after I had lost all hope of resurrecting my keyboard due to an unfortunate encounter with a full glass of Mountain Dew.
At no point did I ever consider putting it in the dish washer. That would have saved me hours!