Ideas are far and away the easy part.
Any idea you present on a public forum such as this should be considered freely given to the public. If they try to present your ideas posted on this forum as their own you can shoot them down with evidence of your postings and their date. To stake a claim to IP you have to go the next step and define an embodyment or create an expression. As far as getting a bunch if IDEA people to work together you might as well learn to heard cats.