I've ordered magnets from K&J Magnetics.
http://www.kjmagnetics.com/They have a LARGE selection and lots of info about magnetics.
I've used them for latches, holding panels on, etc.
Possible use is as large as your imagination.
I can see how large rare earth magnets could be dangerous.
The web site has warnings for some of their magnets.
One has to be careful with the magnets. Letting them slam together can damage them.
Over tightening the counter sunk magnets can crack them too.
On latches I have mounted the counter sunk magnets so I could adjust their position. I did that so when the door closed
the door or magnet did not quite touch the other magnet or steel that it attracted to.
There was no chance of damage when the door slammed shut.
Magnets can be an attractive solution.
Floyd