Methods and apparatus to collect distributed user information for media impressions and search terms

A tangible computer readable storage medium comprising instructions that, when executed, cause a machine to at least:

• receive a plurality of first identifiers and a media identifier collected by a data collector installed at a mobile device in connection with an application, the first identifiers identifying at least one of the mobile device or a user of the mobile device, and the media identifier indicative of media presented via the application at the mobile device;
• generate a plurality of encrypted identifiers by encrypting the first identifiers, respective ones of the encrypted identifiers decodable by corresponding database proprietors to which the respective encrypted identifiers pertain;
• and
• send the plurality of encrypted identifiers in association with the media identifier to an audience measurement entity.