Can allowing toner to get low damage a laser printer?

Just look at how the laser printer works. http://computer.howstuffworks.com/laser-printer3.htm A laser beam create an electrical charge on a drum, this charge attract small particles of toner that are then transferred to the paper. Then the paper goes trough the oven that cook the toner to make it stick to paper. I see no reason why no toner can do any damage to the printer. It will just stay blank.

Do not believe printer sellers. They make no money on the printer but only on cartridge. So they will tell you to change them more often than necessary.

Short answer: No.

A laser printer will have a mixture of toner and developer in its developer housing. The physical interaction between the particles of toner and developer are what gives the toner an electrical charge. The polarity of this charge will depend on the development system being used in your specific printer.

The printer will either have a Toner Concentration (TC) sensor, or use an algorithm to determine how much toner is in the housing, and how much to dispense.

In many home and small office printers, when you replace the toner you also replace the developer as well, starting you with a known TC. If you are actually adding toner, only, then the printer will dispense toner to reach the working TC. I suppose it might take longer to tone up if you really ran it down.

In no case would you run into a permanent damage situation.