This is what we track:
We assign each respondent an id. That helps create separate data entries.
The id is generated when you choose to respond to the survey. It contains no reference to any personal information.
In essence, we only track what we need to produce a good survey.
Task Analytics is a cookie-based tool. We use the cookie _tmc so that users who have either participated already or opted out of participation, are not asked to partake again for a set period of time.
This not only helps create a more user-friendly experience, but also brings more reliable and consistent results.