There are few science fields where amateurs can make a contribution. One such field used to be in discovering new comets and asteroids, but now automated telescopes do the vast majority of the discovering. Amateurs still make a good contribution when they follow them with their own telescopes for a week after, but it's a bit less glamorous. Another case where they make a difference is tracking common birds at birdfeeders in Project Feederwatch.
However, amateur archaeology is a bit less common, and more so armchair archaeology, partly because of the training usually required, and I've never before heard of amateur satellite archaeology, but now some guy's done it, using Google Earth nonetheless. I wonder how many crackpot calls each museum gets compared to how many eventually pan out like this?