I took a bag to the beach, then put my laptop in that bag a few weeks later. The leftover sand (because sand is basically glitter) had some magnetic bits, which clogged the magsafe connector. I had to spent like 20 minutes with a toothpick to get enough out to charge, and it was never quite back to normal.
Strong adhesives are often a good way to defeat magnets. (I've used this principle, but not in the specific context of removing magnetic crud from inside a magsafe plug.) A properly designed magsafe power plug would have a way of either easily replacing the plug or removing/defeating the magnet.