Most good ideas happen when I'm in the middle of another project. By the time I'm able to devote any serious thought to it I've already gone through five notebooks and oodles of scrap paper, so I make a point of entering at least the basic elements of every idea into Workflowy the same day that I initially write it down on paper. Then I have a searchable record, and it's really easy to expand on various points in five-minute chunks or on sleepless nights. That way, whenever I'm looking for a new project I have a bank of ideas to pull back out onto paper.
I also use Workflowy to keep track of goals and sort of the "big picture" TODOs.
I am of the opinion that life is too short to worry, plus people generally aren't able to steal ideas. Execution is always very different. Look at the Xerox-Apple-Microsoft implementations of GUIs... All very different.
My ideas start on napkins or Notes on the iPhone, get translated to Workflowy and then fully drafted and edited into a blog post: http://rayhano.com
The hope is others take the ideas and use them with their own. Ideas should be free, only then can society benefit.
I haven't been sufficiently concerned/motivated to investigate their privacy policy further.
[edit:] https://workflowy.com/privacy/ may raise concerns; I need to review this policy later (and compare it to those of other free services such as Google which I also use).
I love those products that look minimalistic and trivial on first sight but that are feature-packed underneath for power users: full keyboard use, sharing, search & tags, copies/templates, "hidden" timestamps, ...