awesome stuff!
you say that you are no longer working on adDetector "due to potential conflicts with my full-time job". I see you work for Google. Can you elaborate on why the conflict?
When I first read this I thought, why would they start with hotels? may be because the big profit they make out of reservations?
Then I remembered what an accountant friend once said to me: "Hotels are big portals between the black and white worlds".
So you may have black money in bitcoins (and a Hotel which is your "legal business"), and want to "wash" it? now you can do it through Expedia (they having a bite in the process, hence their motivation).
In mid february I created a gmail account and only used it to subscribe to Paypal (didn't touch Ebay). The Paypal account is associated to a NY home address.
On March 15th I received at that email address a "New York Lotto" phishing email. That is the only spam I got so far on that email account.
So I would assume that they have at least some Paypal subscribers data, including email and home city (and maybe address).