Climate scientists certainly wish there was less citizen science. If they wanted to shut up climate deniers (and skeptics) about data, they would do what physicists do - send all 10 billion pieces of raw data. Good luck making sense of that, citizen scientists. Biologists could also likely do with fewer people who know just enough science to be wrong.
But in areas like astronomy, citizen scientists do a lot of good. Sure, they often use Big Science tools to find things - telescopes and experiments that professional astronomers had to fight for and justify - but plenty of people with home telescopes beat the pros to new things.
Overall, it just has to be that an informed populace that is engaged is good for science and therefore good for policy.
Writing at DivaBiotech, scientist...ummm...DivaBiotech (is this 2002? Why is anyone anonymous in science on the Internet?) outlines 5 good reasons why Citizen Science should be embraced.