Why So Much Telemetry ?

This part of the policy sort of addresses your question [edit: make that several users’ question] about how to opt out [edit: and also to know what information is being communicated to “telemetry.” This describes how to ask for it so somebody please say you’ve done so - and later let us know what you hear back.] :

JAMS is the US-based independent organization responsible for reviewing and resolving complaints about our Privacy Shield compliance—free of charge to you. We ask that you first submit any such complaints directly to us via privacy@dropbox.com. If you aren’t satisfied with our response, please contact JAMS at https://www.jamsadr.com/eu-us-privacy-shield. In the event your concern still isn’t addressed by JAMS, you may be entitled to a binding arbitration under Privacy Shield and its principles.

Your Control and Access of Your Data
You have control over your personal data and how it’s collected, used, and shared. For example, you can:

Delete Your Stuff in your Dropbox account. You can learn more about how to delete files saved on Dropbox here.
Change or correct personal data. You can manage your account and the content contained in it, as well as edit some of your personal data, through your account settings page.
Access and take your data elsewhere. You can access your personal data from your Dropbox account and you can download a copy of Your Stuff in a machine readable format as outlined here. You can also ask us for a copy of personal data you provided to us or that we’ve collected, the business or commercial purpose for collecting it, the types of sources we got it from, and types of third parties we’ve shared it with.
Object to the processing of your personal data. Depending on the processing activity, you can request that we stop or limit processing of your personal data.
If you would like to submit a data access request, request that your personal data be deleted, or object to the processing of your personal data, please email us at privacy@dropbox.com. For more information on how to control and access your personal data, please see our FAQ.