Basically, you don't. People come and go from job to job, and keep their experience.

That being said, a very innovative idea is usually quickly copied. Paul Graham reminds how easily he did copy his opponent"s views :

Sometimes, in desperation, competitors would try to introduce features that we didn't have. But with Lisp our development cycle was so fast that we could sometimes duplicate a new feature within a day or two of a competitor announcing it in a press release. By the time journalists covering the press release got round to calling us, we would have the new feature too.

Said otherwise, your edgy idea is an asset only if your execution is quick and flawless, enough to leave opposition behind you. You'll have to rely on technical people for the execution. In your shoes, I'd be far more wary of other firms trying to copy your ideas than insiders getting out and doing the same thing. It may happen, but it's not the most common problem of people with new ideas.

As Joe states in his comment, choose the best, pay them well, and treat them well. Not only it reduces the odds that they'll go elsewhere(doing damage to your business, or simply leaving you without their talent), but it will be known, and it should attract others amongst the best. Which you need, if you want to keep your edgy idea edgy.

Basically, you don't. People come and go from job to job, and keep their experience.

That being said, a very innovative idea is usually quickly copied. Paul Graham reminds how easily he did copy his opponent"s views :

Sometimes, in desperation, competitors would try to introduce features that we didn't have. But (.../...) our development cycle was so fast that we could sometimes duplicate a new feature within a day or two of a competitor announcing it in a press release. By the time journalists covering the press release got round to calling us, we would have the new feature too.

Said otherwise, your edgy idea is an asset only if your execution is quick and flawless, enough to leave opposition behind you. You'll have to rely on technical people for the execution. In your shoes, I'd be far more wary of other firms trying to copy your ideas than insiders getting out and doing the same thing. It may happen, but it's not the most common problem of people with new ideas.

As Joe states in his comment, choose the best, pay them well, and treat them well. Not only it reduces the odds that they'll go elsewhere(doing damage to your business, or simply leaving you without their talent), but it will be known, and it should attract others amongst the best. Which you need, if you want to keep your edgy idea edgy.