I have exactly the same issue (I get an insane amount of email for other Firstname Surname people that isn't me from various other places in the world), but I'm 100% sure at this point that it's people using the wrong email address, as occasionally when I contact the people to let them know they've emailed the wrong address, they have actually told me the real email address they should have used, and they were missing a number, or in one case it should have been an initial instead of the full first name.

I used to also think that Google were screwing up by allowing a 'clash' of firstname.surname and firstnamesurname, and maybe they did a bit in the 2004-2009 period, but with lots of testing over the years (sending test emails to both), I'm confident now it's 'just' other people's emails getting 'simplified' too much when being told, and it ends up being sent to me.

I do however think Google shouldn't have allowed that alias situation to arise.

I also think (based on the fact that my 'un-dotted' email alias has been successfully used to sign up for various services for the other people) that many online services just have very poor sign-up validations of emails.

When I was a kid, I used to get a ton of emails for a guy who put the wrong email address on a dating site. It was always interesting at 13 to have to tell women that I wasn't the man they were interested in.