"Improve compression technology X so that live video is technically feasible sooner than expected"...now that's a great idea. Likewise, "Use marketing technique Y to create an insatiable demand for personal web cams", also a great idea. Someone starting a company in a given space that think will take off doesn't really constitute a groundbreaking innovation, though it is a smart business move.
Many if not most people who say "I have great ideas all the time" are overvaluing the quality of their own thoughts. Plenty of people have good ideas every day. But truly great ideas, by definition, are rare. Not 1 in 100 rare. More like 1 in 1,000,000 rare. And it can be really hard to tell the difference between the two, especially when evaluating one's own ideas.