I've been wondering this for a few years and the Internet has never given me a clear answer.
Do you still send a gift when you receive an invite to a wedding that you won't be attending?
In the past I've always sent gifts for out of town family, close friends when I couldn't attend due to business travel, etc.
When I've received invitations from people who I haven't really been friends with since middle school I usually promptly decline with a nice note that I won't be in attendance, but I don't follow up with a gift. (I would never dream of inviting people this far removed from me to my wedding.)
What's the norm for this?