you could apply this idea to lots of other valuable objects, too!(1) find a way to make your expensive luggage look grungy and not worth stealing(2) disguise your rolex watch as a cheap Casio, with a fake front over it(3) cover your expensive video or still camera with a fake cover that looks like a disposable Kodak(4) and of course design a container for your lap-top computer that makes it look like a take-out pizza (although a really desperate thief might be tempted to steal it anyway).

Hmmm where have I heard of this before... One of William Gibson's books (all of which you should all go read, by the way). One of the characters is a bike courier and she applies some kind of paint to an expensive carbon fiber frame that makes the bike look old and rusty. I don't think that there's a product that does this today, probably the closest I've seen is this Half Life 2 PC case mod. Two or three different kinds of paint and some creative sanding made this PC look old and rusty.

The problem with this strategy is that it would only fool the least knowledgeable bike thieves. Anybody experienced with bikes can tell you which parts are expensive and which are cheap.

If I see that you have a $400 set of wheels, $200 cranks, and $120 pedals, some sloppy paint on your frame isn't going to matter. Any smart bike thief would know how much each part of your bike would get on Ebay or at a swap meet.

Your frame might be worth less to a thief after you paint it, but since the frame is usually the only part of your bike with a serial number, a smarter bike thief would probably just scrap the frame and sell off your components piece by piece. Once they're removed from the frame, they're completely untraceable.

Just don't let your bike out of your sight, ever, and it might not get stolen.

Here's one idea: http://www.sprayonmud.com .

Here's a much better one - lock you bike in front of a window or in an area that is supervised or has video surveillance. When the local Ikea opened, I saw that their bike rack was tucked into a corner of the building with no windows. I called the manager and complained and said I wouldn't be able to shop there unless a more safe rack was provided. One week later they moved the rack so it is directly in view of the front of the store where they have security. At my job we get regular memos about how we should bike, carpool, bus or walk to work to help the environment, it took me about a year of regular lobbying before they put in a secured, card-access only area for employee's bikes. Be persistant! Speak out! The more we do this the better things get.

I don't get it, What's the point of getting a really expensive bike because of the looks and then make it look like rust? Then why do you get it in the first place? You could have just bought it second-hand. Even if the quality remains unchanged, I know that at least 30% of the reason that i want to buy an item is because of the looks. Maybe if the paint changes color when you get nearby or when you don't use it for a long time it might work. Still, i don't know if it's possible or if it's feasible.

I don't think this is a bad idea, but there might be better options. An alarm or "lo-jack" style tracking device might be better. However, your idea wouldn't add any weight and would be inexpensive to do. It might not fool a "professional" bike thief, but really most bike thieves aren't professionals. I actually had a friend when I was a teenager who did just what you are suggesting, though his bike wasn't expensive to start with. He just didn't want it stolen.