I don't feel the same loyalty to the people who don't have me on their reading list. Sort of like eavesdropping on a conversation in a public place, I don't feel the need to excuse myself when I move on.
I'm pretty much an auto-friender: I'll add you and keep you. So far there are only (3) reasons why I will not add/trim someone from my list if I'm on theirs:
1) You have a read-only journal. I figure you're only here for the fannish stuff. Plus I don't know who you are; you could be anyone. *paranoid twitch*
2) Your journal fluttered to the ground and died. Dead journal, so sad. I consider any journal inactive for 12 months dead. I call it and turn off the crash cart and defibrillator. I've got one or two that I've hung onto that are deader than that, my BFF in RL being one of them. But after 24 months, I'm going to give up all hope and declare them dead and delete. My BFF! *cries* Penelope was a stronger woman than me.
3) You deleted your journal. Where are you? Come back! I'll have to take LJ at their word though and assume they've erased all trace of you after 30 days. After 30 days, I'll do the same. Sorry. I'll wear my bestest black t-shirt for you.
ETA: Every day is defriending amnesty day here. If we've interacted a lot, I might shed a tear or two, but I'm a big girl. People and interests change. It's okay. If you're hesitant because of the birthday thing, I do that for everyone--BNF and not-so-known alike. It's just my way of saying "Happy Birthday!"