Most easy and cheap protection against bee theft?

[Michael Bush]

My brand was not cheap but it was worth it.  If I only had four or five hives, it probably would not be worth it...  Back when I had two, I free formed the brand with a torch and a soldering iron.  It was very time consuming...

[chux]

The thief will be a beekeeper. If your hives are off the beaten path, he will have plenty of time to defeat any security measure you employ, with tools from the hardware store or his shop. He will not be fooled by signs about killer bees, as was stated. You have no way of tracking these hives once they are moved, unless you could hide some form of gps tracking device within the comb of one of the frames, where it would remain undiscovered. At best, locking the hive down could slow the thief or encourage them to look for an easier target.

So location is the first key. Put your hives where nobody will know they are located. Way off the beaten path. Or...put them right in the backyard in a neighborhood where everybody can watch them for you, and the dog can warn you if they are being stolen at night.

Branding...Why brand equipment? Hopefully, the thief will try to sell your equipment, and someone will recognize and report your brand. But what if he never let's anyone else see the equipment, running it in his own yard? Pointless to brand in that case.
And what are you going to brand? If you brand the box, a thief can sand the box down, putty the branding, and then paint. you can brand each frame. Maybe that would effectively deter a thief if he were to look inside the hive before stealing it.

I think the best idea is to use a game camera. You can get a decent game camera pretty cheap now. Get a few cameras that are motion activated, and set them up. If anybody comes calling, you can get them on camera down the path, coming and going. Get a license number. If I were going to spend money to secure hives, that's what I would do. If I could hide a camera well, by the path, I might even post a sign near the hives telling a would-be thief that I have multiple cameras on property and that they are already caught on camera. This would be a strong encouragement for them to leave my equipment alone.

[Steampunked]

I have a wood burner, which wasn't as expensive as a brand.  I wrote my number inside each box, under each box, and on each frame, and then painted them on the lid and outside.  It only took me a few minutes by hand, and the wood smelled nice anyway.

Someone could certainly sand everything off, but it would be awkward for them without taking the boxes completely apart, and I put my brand on the more delicate parts of the half-frames I use so that sanding them roughly has a good chance of destroying them.

Probably would never be relevant, but my boxes are also branded inside the joints I nailed - which is much less likely to get found, but would be good for proving a box is mine.

[BeeMaster2]

We had a police officer Beek that was caught because he stole hives from a state run program that had branded the sides of the frames. They didn't even know they were stolen. He just took a couple of hives from each site and they didn't realize it. The bee inspector saw the brands during an inspection. He didn't say anything and started an investigation.
Jim

[George007]

Thank you all!

[Hops Brewster]

I keep just a few hives.  I use a wood burner I got at Harbor Freight for around $6 to burn in my brand, which is my initials in a distinctive pattern on the boxes and frames.  My state registration number is on the boxes.
The initial chore took some time, but I now only have to use it occasionally as I add or replace parts.

[Richard M]

One of these could be handy http://www.save-bees.com/en/save-bees-products-2/beehive-anti-theft-tracking-device/

Probably too dear for every hive in the apiary but place one in one or two hives, assuming the thieves nick the lot then they'll take it with them. Beauty is that there's a movement sensor, so you get the warning straight away or if in a very remote area, as soon as the unit comes within mobile phone range.

[NeilTheCop]

Adapted from Mr. Jeff Foxworthy, but very valid out here in the wilds of New Mexico.

"You come up on a house where the grass is this tall, and there's a dog chained to the clothesline, and a motor swinging in the tree, buddy, that's a house where a gun lives! And if you want to find out what kind it is, just try and steal a beehive after dark." 

[Oldbeavo]

Identifying hives is not a deterrent to theft, the honey and the bees are transferred to other hives of the thief and the boxes are burned. So ends the tracking with the brand. The value of honey and bees is what makes them stealable. Anchoring is not feasible in big numbers, 140 hives went in one go in spring.
Many are using security cameras to try to identify the culprits, about $70 -100 US will get you a reasonable unit.