In reply to Miroslav Glavić.

Yes and no. Certainly most volunteers cannot spend great swaths of time on such things, but it is amazing how much motivated volunteers can accomplish—just look at something like Occupy Sandy, or indeed, so many WordCamps. of course, some volunteer tasks are more rewarding thian others, and often working in groups makes the less-rewarding tasks more congenial, so I think generally a mix of paid/volunteer folks working together as equals (with those with the most time, generally the paid folks) coördinating for continuity can accomplish a lot.