According to the National Fire Protection Association (NFPA) in the Untied States:

• In 2010, an estimated 16,800 reported U.S. non-confined or confined home structure fires involving clothes dryers or washing machines resulted in 51 civilian deaths, 380 civilian injuries and $236 million in direct property damage.
• Clothes dryers accounted for 92% of the fires; washing machines 4%, and washer and dryer combinations accounted for 4%.
• The leading cause of home clothes dryer and washer fires was failure to clean (32%), followed by unclassified mechanical failure or malfunction (22%). Eight percent were caused by some type of electrical failure or malfunction.

I could not find any statistics for Canada but we could probably estimate the the numbers are about 10% of the U.S. numbers according to our populations.

Thankfully it seems that to have sunk in to most people that it is important that the venting from the clothes dryer should be non-combustible and clean. Here is more guidance in that regard.

The reference from the NFPA above noted that 8% of the fires were caused by some type of electrical malfunction. Not well known by the public but encountered by home inspectors from time to time is a defect in the dryer electrical breaker size.

For a number of years in the 1970’s and early 80’s it was common for electricians at least in some areas to install 40-amp breakers for the dryer circuit. This was likely because older dryers which would have been in use at the time would often overdraw current and trip the standard 30-amp breaker.

It is and has been standard for some time to install 30-amp breakers for clothes dryer circuit. The wire size (#10 gauge) and the dryer outlet are usually always rated for 30-amps max. The concern would be some kind of malfunction within the dryer could cause more current to flow through the wiring than it was meant to carry,  thus causing a potential fire hazard.

Fortunately, this is a relatively simple defect to correct. If your dryer circuit is protected by a 40-amp breaker, you should have it changed to a 30-amp breaker. This is true even if you have a larger gauge wire that is rated for 40 or more amp since the dryer receptacles are almost always rated for 30 amps. As well, the manufacturer instructions for most all dryers mandate that 30 amp breakers be utilized.

Clothes dryer outlet with 30-amp rating