"Can we actually trust any of the mega corps to remove the data"
Of course no. Ebay, for example, terminated my account because I didn't use it for a while. I wasn't unable to reset the password using the username or email, but when I tried through PayPal, it returned as the account name as <number>@deleted and the email address I used - but it didn't re-activated the account and suggested me to call support. It is clear the account wasn't deleted, and my data still there, although not accessible by me. Guess I will go through my country privacy law to ask for a full removal of my data, and see what happens...