I have an idea for a gamification/human-computing application/service which can be used to solve an AI-hard problem more efficiently, like reCaptcha.
I can build and promote it, but I'm worried once it prove to work, larger companies simply copy it to their own advantages, and I won't be able to profit from it.
Is there anyway to protect it or how to profit from it?
Patents can help, there might already be a patent out there and if your concept has anything to do with mathematics it probably can't be patented. They can also cost a lot to enforce. My suggestion is become the leading thought contender out there as soon as possible. Large businesses are slower to move and are less willing to take on risk. If you establish yourself as the leader in this business what will probably happen if a large company wants to enter the market place is that they will buy you. Its much easier to purchase a working model then spend the time and take the risk of innovation.
Keep things secret and get non-disclosures when working with outsiders , this is the poor-mans version of a patent.
Grow as fast as you can , the larger your footprint the harder it would be to unseat you.
Add perks and features, the more rounded your product the more your competitors will have to do to catch up.
Build your brand. I could compete with Coke maybe even copy their taste but it really wouldn't matter I can't compete with their branding capabilities.
Last but not least don't let fear of competition stop you from allowing the world and yourself from benefiting from your idea. Competition will come and it will suck when it does at first but use them to your advantage and enjoy what you do.