Amateurs CAN do science. It's been very successful in fields of astronomy, palaeontology, bird counts (Audubon does these surveys with backyard birders) and various individuals finding something unique and taking it to people who are qualified to look at it. The problem with amateur cryptozoologists (paranormal investigators and ufologists) is that they have their own insular community that is shut off from science. There are many skeptics and scientists who would help them understand the "evidence" they are collecting but various roadblocks exist to cooperation.

(I am the author of the linked piece, BTW. There is a longer piece on amateurs doing sciencey things in the Mar/Apr issue of Skeptical Inquirer.)