[Clark Pappas]

It would help if we knew what the application was. Covering some bases...
*If you want to secure down a component: I'd say go to a local hardware store and get some Velcro. My two cents.
*If you want hold frame members together: Not at all stable, and probably not safe. Find a different way to attach them.
*As a covering: Id say ok on anything that doesn't involve electricity.
*As a marker: We do it with our wiring. A parent gave us some gaffers tape, and we mark different wires and components with a certain colored tape, so we can easily determine which thing is attached where. Although it isn't necessarily duct tape, duct tape can be used in the same manner. besides, as far as I know, duct tape colors are far more widely available than, say, electrical tape colors.