I think the odd one or two at each gig are ok. When he first started out it began to get ridiculous; the man could hardly sing for being held; did Jesus ever have this problem?
This is why he has the lovely, but firm on-stage security that he has now, to stop potential incidents, like last night. There's not just the people to consider either, think about all that electrical equipment; if some rabid fan were to crash into a speaker or over a wire the whole gig would be interrupted.
However, the fanaticism is part of the reason I attend more than one gig during any tour; I love being down the front amidst a bunch of sweaty devotees all crying out for their hero. It's tantamount to a spiritual experience.
Just for the record, I had the chance to invade the stage myself last April; I was lifted above the crowd by two guys, there were no barriers, the security at the front actually let me lean on his shoulder in order to reach out to Moz and I had one foot on the stage. With hindsight, I should have gone for it so I could have hugged Morrissey, but the fact that he walked right across the stage to take my hand in the middle of a song, and allowed me to kiss him made me want to respect the boundaries.
I think I'll leave the invasions to braver souls than myself, because usually he enjoys the madness of it, but there's always one or two that end up catching him at the wrong moment and pissing him off; I wouldn't want that to be me.