A subscription pay wall would give the most noticeable drop in duplicate accounts. As long as your service is free and account creation is simple (which it shou

A subscription pay wall would give the most noticeable drop in duplicate accounts. As long as your service is free and account creation is simple (which it should be), you'll get duplicates if there's incentive to do so. Things you can check if you want to prevent dupes: (But be aware that some of these can and do target legit users) - IP checks - Browser Cookies (if same value for multiple users) - Flash Cookies (same principle) - E-mail - System-specific metrics (if you're running native code)