"we assigned everyone 9 digit phone numbers, but that ran out after 50 years of population growth led to over a billion people. Now we assign everyone an 18 digit phone number. Personally, I'm worried we might run out in another 50 years."
I mean as long as you can still set your email-number to whatever you want and update it if you want to drop the old one.
I feel like there's also implications for spam, like you want to target X demographic, all you have to do is try numbers with common name combinations from various cultures. Like in Nathan For You when he made a targeted billboard for a psychic that said "Maria Garcia, I had a dream about you" so all the Maria Garcias who saw the sign would become potential customers.