I personally would not advise swapping pedals on a daily basis. However, it is unlikely that you'll do much damage to them if you do. You'll probably shorten the lifetime of the threads by quite a bit though. You will want to use a high-quality pedal wrench and always remember to grease/anti-sieze the threads. I prefer Ti-Prep. Even if you don't have titanium spindles, it's good stuff and the bronzish colour looks pretty cool.
