Add a "notARobot" field to Google Plus OAuth tokens for users who have paid money for Google products
Bot accounts are a big problem for apps and social media sites. One effective means of combating these is to subject users to captchas, which is not ideal for user experience, and it is sufficiently cumbersome that it is almost never used for frequent actions such as voting. Another method is to use email verification, but this is not terribly effective as the cost of creating an email account for a bot are very low. To be effective, bot detection mechanisms need to be high-cost to circumvent. Fortunately, many people with gmail accounts also have spent money on Google products such as Google drive, which should be sufficient to show that they are not low-cost bot accoutns. If one of these users tries to log into a third party app using a Google Plus OAuth token, Google should be able to provide a "notARobot" field on that user's OAuth token. The app could then recognize that the user is definately human, and treat him as such.