Well, I haven't in about three years. I guess I lost the calling. But the article linked explains the reasons why, why not, and how to play the four strings. Plus some bonus video.
I (used to) play the electric bass. It's not a bass guitar, although everyone calls it that. There actually is an instrument called a "bass guitar." It has six strings and is tuned lower than a regular guitar, but it's not a bass. A bass is that doghouse with the four strings. The electric kind hangs on your neck and gives you a bad back (left side), deafness, and a couple hundred bucks a night for as many nights as you'll show up, because every other person in the world is an unemployed guitar player. Own a bass and you'll always work.