David I must admit I agree with many of the points Alex made, especially point 3 in that I suspect many "professional" astronomers may not wish to have their professional world intruded upon by amateurs - those who have no relevant degree, and who "have not done their time" as such working their way through University studies and through the professional ranks.
I personally DO think amateurs may have much to contribute - simple current example being Terry Lovejoy and his namesake comet.
I suspect that point 2 (how to contribute in a meaningful way) has some truth as well. I think that should an amateur comes up with something of value to contribute it may attract the interest of some pro's, but that isn't collaboration is it? Collaboration implies planning to work together / share results / etc in advance of the project, not simply using any possible gains afterwards.
I would enjoy the opportunity to get involved in some sort of collaboration, but to be honest I haven't seen any pro astronomers asking for assistance of late.
