At least according to http://theodoregray.com/periodictable/Elements/031/index.s7.html gallium and at least some of its alloys are really sticky, leaving residue on most anything. "Unfortunately, it stains your hands and is hard to get off, so I don't recommend it. In fact, it stains or sticks to just about anything, which is very irritating because it would otherwise make a very nice substitute for mercury where a liquid metal is called for."
I've used one of those gallium-containing fake-mercury thermometers myself, and after a few uses the liquid metal got stuck to the glass tube, and it never worked again. They could have made some better alloy of it or something, but that's not mentioned in the abstract, at least.
(Also, someone is actually using Medium? Impressive, I was compelled to use it for a course, and it was the most dead "social network" I've ever seen.)