What's wrong with my cactus?

A friend gave me a cactus last summer. It appeared to be healthy when I got it, but now it's developed brown spots. It's not very big...only about 9 or 10 inches tall. Is it what's known as 'scale', & if so, can it be saved? Also, can anyone tell me what kind of cactus this is? I've posted a picture of it on my blog here: www.whatsbeckydoing.blo.com.