There's been a big kerfuffle over at the forum at acousticguitar.com recently about polishes and the harm that they'll do or not do. Check it out and draw your own conclusions. The only thing I wouldn't put on a guitar is anything that contains silicone. Not that it would hurt the guitar in ANY way, but that it contaminates the surface of the lacquer with minute bits of silicone which are almost impossible to remove. The problem arises if the need to refinish ever does arise. The bits of silicone will float to the surface of a newly applied coat of lacquer and affect the surface tension of the liquid coat and cause a "fish-eye". Almost impossible to respray without adding even more silicone to the mix to even out the surface tension of the entire coat. It's an evil cycle. "Pledge" and other such furniture polishes are the chief culprits. Avoid them on your guitars!