Microchipping Question?

There's a local event coming to my area that will microchip my dog for only $20 (they're very reputable and it's a special offer kind of thing). I've been considering this because I love my dog so much and if he was lost, I'd definitely want him found and brought back to us. A friend of mine bought a dog from a breeder a few years back and said he came microchipped but they never activated it because there was some sort of monthly or yearly charge to keep it active. I guess kinda like lo-jack for your dog or something. Does anyone know if that's true? I thought microchipping was just a "tag" placed under their skin that vets offices and shelters and the like can scan to locate info. Does anyone know?

I work with a rescue and we chip all of the dogs that are in our program.

In addition, all of my dogs are mircrochipped with Home Again Microchips. There is another company - Avid.

Home again is changing the way they run their program and they can't seem to decide if they are going to charge a one time fee (which is what we have through the rescue and what I had for my dogs) or a monthly fee.

This is a great service in case your dog ever gets out or slips his or her collar. The more ways your dog can be identified and returned to you, the better. The best bet you have is keeping a collar on your dog with a tag. However, some dogs can slip the collar and get out. It happens all the time.