In Boston, it's ticketed-passengers-only at B, D, and E but anything goes at C. At A, I forget. There's no correlation that I can detect between policy and line length. Regarding having to check in before passing security, one tends these days just to have to show a ticket OR bp OR e-ticket receipt to get by. Funny thing is that back in the early days of e-ticketing, C was ticketed-passengers-only as well, and security was reluctant to pass passengers with e-receipts: I think it's this that led to the current laxity there.