I wouldn't mind, we all have secrets and it's up to us personally to decide with whom and when we share those secrets if we decide we ever want to share them.
Not telling every detail about you life isn't the same as lying, especially when it comes to just online friends: I'd say it's even safer to keep some things to yourself. :-)
I'd be disappointed and they'd be gone.
You never know who is who.
Yes, that would upset me, for sure