Funny thing is that a lot of people don't know that relay contact composition is different (and is usually mentioned on the relay's datasheet) depending on the type of load (most especially resistive vs inductive). They then wonder why when they use a motor on a particular relay, even with a snubber, the contacts stop working.

Relays are great though for motor controllers, especially when you need higher amperages (and don't want the huge expense a mosfet solution can sometimes bring); an h-bridge is very simple to build, and tying an n-channel mosfet (of appropriate amperage capability) on the low-side between the relay(s) and ground, and you get easy PWM control (just don't switch the relay while PWM'ing of course).