Ask HN: Startup Vacation Policy

My company is getting to that stage where we have a number of salaried and part-time employees. My partners and I are looking to encourage and reward our employees while building an open and inviting company culture. At the same time we want to make sure and protect the company and make sure this environment isn't take advantage of. I've read of great companies with relaxed vacation policies and I've also seen other established companies with more traditional policies. What has HN found to work for you personally as an employee or an owner?

As this is HN, any links you've found to be helpful would be appreciated as well.