Nah - security is a myth
I once *seriously* pissed off the people at the data center in Vauxhall (you know who you are) when a sales director was trying to pitch more service at us after the company had been annoyingly slow in delivering what we needed (nothing evil, the usual bureaucratic nonsense).
In the middle of an increasingly boring meeting he decided to use me to sell for him by asking what I thought of their data centre as I'd been there the week before. When I agreed with him even my line manager woke up because it's not my habit to be complimentary, so they knew something was coming (I have a bit of a reputation for pranks anyway).
By pure chance I had amused myself that day by signing in as Fred Flintstone because nobody bothered to check ID, and my colleague had nicely played along by not even blinking and just signing his name.
So I mention this, the guy goes bright red and most of my colleagues fall over the table laughing (my only defence is that the guy was seriously irritating and had invited himself so - to me - he was fair game). An hour later I get a call from the guys at the hosting company asking what the hell I've been up to (we had quite a good working relation, just some directors were idiots).
On enquiring why, he told me that the whole club of directors had just gone into session and he'd heard my name and my company be uttered a few times, loudly, in what appeared to be a serious bollocking :-). When I told them it emerged we shared a dislike for that sales director, and I heard later they didn't exactly let him forget this :-).
Next time they DID check ID, of course, but I know from experience that it'll wear off. Otherwise I wouldn't have been able to walk in and out of the London Stock Exchange building for 2 weeks without showing a badge either. It's a bad habit, I admit, a sort of social engineering for beginners. It's not hard to do at all once you've worked out your fallback strategy (with the LSE I had the badge actually in my pocket, I was just checking how long I could get away with 'forgetting' it).
Note: all of this was quite a few years ago. They *may* have learned eventually, and it's worth noting that at Kings Cross there appears to have been threats of violence (it seems unlikely people allow themselves to be tied up otherwise). I personally wouldn't risk my skin for some overinsured piece of kit either, and if nobody thought of installing a silent alarm trigger I would want to have a word with the security manager there afterwards..
What amuses me, though, that this has happened in the city of CCTV and nobody seems to have a clear picture of the bad bogus bobbies.
Now, does anyone know where the Paris Hilton film studio is?..