Oddly this is almost a non-issue since Gmail has already basically solved this problem by allowing you to add only certain addresses to “My Contacts”.
Before “My Contacts” was an option literally every email sent was bunched into one giant group which made it nearly impossible to try and sync your Gmail address book to any mobile device without having thousands of contacts.
Fortunately if it’s still something that happens to be a pet peeve of yours you can now go in your general mail settings and turn off the the option to auto save all email addresses.
Personally I find that now that I can control which contacts get stored in My Contacts, which is what Gmail uses to sync to other devices, having all the other email addresses stored in there doesn’t bother me and does occasionally come in handy when trying to locate an old contact that I haven’t emailed in years.
What do you think? Will you be shutting off your auto-save function or keeping it on as a virtual archive of literally everyone you’ve ever sent an email to?