I "concede" that they are doing nothing wrong and you are way out of your depth here.

I strongly suggest that you drop this before digging yourself an even deeper hole in front of the people following this from Twitter.

That's a value judgement you have to make, similarly to using any service hosted by someone else.

1) Is the potential loss of privacy worth the advantages of the service?

2) Do you trust the company providing the service?

3) Could you do a more secure job of it than the company?

It's not a service I would personally use, but I have no reason to think the company providing the service doesn't know what they are doing.