I cam here to say exactly this. They locked my account while I was on travel internationally.
When did you sign up for gmail MM/YY? Uh, after 2002 but before 2008.
What are three tags you've applied to your email? TODO, NotSpam, ImportantInfo....wait no To Do, Mostly no spam, Saved info... no it was soon-to-do, Unspam.
When did you last successfully sign in to gmail. yesterday afternoonish or morning, is that in the future from this time zone? no wait, I did only work email yesterday? Does my phone's mail app count?
Who are three people you commonly email. Jim69@yahoo.com, oh wait he moved to some leetified version of jimmyjimmy@gmail.com now, but I can't remember because I've just typed jim into the "to:" field and gmail knew who to send it to, (tines 3)
This's why I have a gmail account, dammit! To keep track of contacts and dates for me. If I remembered all this stuff, I'd just use the free email provided by my ISP so people could send me messages.
Needless to say, I had to wait to get to a country, which I guess has fewer gmail attacks, before I could use my account again. I did remember my password though, I remember my last 3 passwords and more if you allow me natural human memory loss (was it @mailPass3? or @mailP4ssThree,)?