Not really although i can understand it if they have spam issues like invisionfree forums although if a phpBB3 has it enabled then it is annoying as there is no point really as spammers can't sign up.
can't invisionfree forums have CAPTCHA then
on my friend's IF forum it was quite funny because a person kept registering on ONLINEPHARMACYCHEAPPILLS or something like that.
It didn't really matter as it was only us who were active members (Mark from hireem and driver from advertisement centre joined but never stayed active)
I can't stand admin validation, but I don't mind the activation emails. If a forum I register on has admin validation, it usually takes anything from 1 week to over a month or more for my account to be activated.