I've only ever switched my router off using the power button on the back. As the router is in a fairly awkward position I was wondering if it would do any damage to turn it off at the mains instead of using the built in power switch?
Further to Jeffers22's comments, it also releases bandwidth for others to use, when you don't need it. After all, it's no use complaining about charges if you have it switched on 24/7 and then your ISP raises it's tariff to covers its increased costs! It's one thing for a commercial operation to have it switched on H24, but generally quite unnecessary for private users.