True fans, without a doubt. People who are interested in and care about your product will send you comments and ideas, and will evangelize for you. That is, as

True fans, without a doubt. People who are interested in and care about your product will send you comments and ideas, and will evangelize for you. That is, assuming you care about making the best possible product. If you're just looking for something to monetize and/or flip to a VC, a million idiots is great.