I like to trim mine off just because you don't get much bark where there is a lot of fat, and there's generally enough internal fat to keep it plenty moist!
On the other hand, we don't waste a bit. I freeze the trimmed fat, and when I have enough, I cube it, throw it in a big pot, add enough water to the pot to make it about 2 inches deep, and render it over medium heat (the water content keeps the fat from getting too hot)
Last time we did this, a few weeks ago, we got 3 1/2 pints of rendered lard, and a big pile of cracklins! GREAT with a little hot sauce! And the lard is great any time you want to saute anything in oil, or especially in pastries or bisquits!