I will always chip every single one of my animals, unless I find solid, scientific evidence that there are harmful effects to microchipping. The rescue that I work with chips all of the dogs that come through the rescue, and register themselves as a secondary contact in case the adoptive family (who is the primary contact) is unreachable. Collars can be taken off, but a microchip will be around pretty much forever unless it migrates or doesn't scan properly. And as someone who volunteers in a shelter exam room, we scan every single animal that comes in for a microchip, so if an animal with a chip gets lost and ends up in our shelter, there is a much higher chance that you will be reunited (as long as you register the chip and keep your contact info up to date - lots of people forget to do that).
If the chip company goes out of business a microchip scanner should still be able to detect the presence and ID # of the chip. It would just be harder to trace the owner, but not impossible I think. I don't think that's a very common thing to have happen either, especially if you stick with one of the bigger microchip companies like HomeAgain.