"What do I have to hide?" was always the response...
[0] http://googlepress.blogspot.com/2004/04/google-gets-message-...
Edit: It's possible my concern was the subdomain and my memory is off. It moved from a subdomain to a /gmail at one point (or something similar). That is when I swore off it.
What clearly recall is that there was something wrong, either it was how it did a redirect to google.com first and then back or shared cookies in a very sneaky way that alerted me. (I was building sites at the time and I was privacy conscience early on in my career)
> As of 22 June 2005, Gmail's canonical URI changed from http://gmail.google.com/gmail/ to http://mail.google.com/mail/.
As you can see from your own source, the canonical URL has always been under google.com, not under gmail.com.
Edit: the parent post was originally linking to https://en.wikipedia.org/wiki/History_of_Gmail, before being edited
Therefore, gmail.google.com could track cookies and activity via google.com.
This has been fixed since then, so I think the memory of the internet is short and wouldn't understand how bad this was in retrospect.
(my previous edits: Yep, I didn't want to drag this out. My memory was off on something.)