Re: Security? We've heard of it.
"Regardless of all the stuff about VLANs, you could check out the building remotely and use the information to find out the best route and time to break in, and delete the evidence afterwards."
No, you just wear a balaclava. Done.
Nobody in their right mind will break into a building and then try to hunt/destroy the cameras. Mostly because they'll almost always be synced to off-site storage, cameras often comes with SD cards inside to double-record all footage nowadays, and the actual reliance on "roll the camera back" is fading fast in favour of "the camera just texts me when it detects movement on an internal camera, with a copy of the last 30 seconds of the footage" (note: all perfectly viable without third-party cloud servers).
Honestly, if it's an average private home, the police don't even have the time to obtain footage and unless they pull up with their car number plate facing the camera, or look up into the camera, you stand precisely 0% chance of identifying them. (Source: Three police incidents of burgled neighbours with captured footage of vehicles and burglars).
If it's any property that you need to keep more secure, that footage is stored in a secure location and mirrored (you tell me where that network cable I plugged into the camera is actually recording TO... could be anywhere in the world, synced to an off-site backup, sitting in a cabinet anywhere on site, accessed live over a VPN, etc. etc. etc.). You'd have to smash all the cameras you passed (which is why they are vandal resistant), pull them off the wall, destroy the cards inside them, find the NVR (or NVRs!) on-site, destroy them too, and hope that in all that time it never got to send out a single message, alert, alarm signal, footage or backup off site.
P.S. any modern NVR has "camera blackout" alerts that can detect obscured / disconnected cameras and alert you in a number of ways. You have from the time you smash the first camera, until the time the security company van arrives to destroy all traces of the CCTV system.
P.P.S. CCTV is not there to roll back and see what people did. That's just one function. It's there to alert someone to something unusual. Like burglar alarms - there's no point getting home and the light is flashing and it's been going off all night and everyone ignored it. At that point you KNOW you've been burgled. You fit a burglar alarm to alert someone who'll do something about it quickly - like your neighbour (highly unlikely), a security firm (better, but expensive), the police (yeah, right, they don't even come out for persistently-ringing alarms any more, they tell you to call Noise Abatement), or... the best option in the world... you. By texting your phone and saying "Internal camera detected movement" or "Lost contact with Front Camera".
You have to notify the only person in the world who care about your property - which is you. That's the function of CCTV, burglar alarms, car alarms and anything else. Everything else you might "think" will happen is a nonsense. I hear a car/house alarm literally every night. I do precisely zip about them. As do all my neighbours. (Source: three house burglaries, nobody "heard anything", several site intrusions, vandalism, burglaries, thefts, not a single one caught in the act or discovered until the next morning).
I supply CCTV footage from large sites to police. Pretty much, it's useless and nothing comes from it. (Source: Three house burglaries, plus dozens of site burglaries and vandalism: convictions - zero, arrests - one [a teacher that was arrested for restraining a teenager from beating his mate up, I kid you not, the guy was never able to work in a school again], time spent - literally MONTHS of hunting footage).
The reason it's on the wall is so that people can see we're watching, and so that the guy who's in charge of the site at night can see whether the banging outside is a gang of kids, or a loose fence panel before he puts himself in harm's way. I guarantee if there's someone actually doing something, he will call the police, but only after he checks the LIVE footage. The historical footage is there for a court many months in the future, if necessary, and is usually so pitiful as to be useless.
If you don't know this, I suggest that you've never managed CCTV or been asked to provide footage to police after an incident. Note also: Approximately 70-80% of the thefts, break-ins, vandalism, intrusions, etc. that I've ever dealt with in my professional life - there is ZERO CCTV footage, even with dozens and dozens of cameras around all the places I've worked.