In today's 365 Days of Astronomy podcast, Mike Simonsen talks about whether visual astronomers (those who use their eyeball, not photography or digital imaging, to make measurements of the brightnesses of stars) can still contribute to modern astronomical research. And the answer is, yes, even in this age of robotic telescopes, all-sky surveys, and computerized cameras, visual observers can still make valuable contributions. If you haven't already listened to the podcast, go listen, and see if you agree. (And, while you are at it, subscribe to the podcast so you can get a daily dose of astronomy through the end of the year.)
Mike covers all of the arguments pretty well, so I have no real points to add. Amateur and semi-professional astronomers contribute in a lot of ways to professional research, from studying nearby stars to studying distant galaxies. There's a lot of important, fundamental work that would not get done without their help, and I think most of us professionals realize the amount and quality of the work this unpaid workforce does for our science.