What I've always wondered is that wouldn't very tiny molecular mechanisms get problems with "accidental welding" since a part could be permanently destroyed by a few molecular bonds forming or breaking and (IMHO - this is my guess/assumption) such events would be likely at e.g. room temperature.
Unless designed well, yes. Parts that move relative to each other need to be designed so that unwanted bonds are unlikely to form. This generally means designing them so that unwanted bonds are less energetically favorable than the bonds they start out with. Of course, as temperature rises, the chance of breaking existing bonds rises, as does the chance of forming new unwanted bonds.
