In reply to Cavalary.

Opt-in does not mean hidden. Apple, for example, asks you to allow it to gather data when you setup a new iOS device or Mac. They make the choice obvious, they explain what it will do in brief and they don't bug you about it. Some people allow it, some disable it. Enough people allow data collection to happen that they get a representative sample.

WordPress would too - you don't need a majority of users to allow data collection in order to see valid results, you just need a sample that represents the various uses and for the sample to be large enough so that it's statistically valid. Given the size of the WP community none of this will be a problem if it's done right.