I dont bother with a hop bag when using pellet hops but with leaf hops I've learned, for me, its a necessity. In recipes that used 4 oz or more of leaf hops I was losing up to a gallon of wort from saturation. Now I just lift up the bag, and give it a nice wringing out, and would only lose a couple of ounces of wort.
I think this one is personal choice. I used to never use a hop sack, but got tired of the trub getting stuck in my auto siphon. Lately I have been using a hop sack, and am pleased with the results. Like Beeropolis said, makes it nice with whole hops. But, I like the way it works with the pellets as well. I haven't noticed a perceptable change in bitterness.
I am kinda new to homebrewing, I have made about 5 batches of beer using the Brewer's Best Kits and one issue I keep having is during the boil the hops spend a lot of time not in the wort. They ride the boiling bubbles onto the side of the kettle and I keep pushing them back down.
1. Is this normal?
2. If I were to use a hop bag would it lessen their flavor (I like hop flavor...a lot!)
I agree that there is no correct way. Having said that, I use bags because they reduce the chance of a stuck transfer and lower the sediment in carboy. If you ever consider a plate chiller, you will want to transfer the clearest wort possible (to prevent clogging it).
I think there is nothing wrong with a 'muddy' wort, but a clear wort lends itself to simple transfers, which speeds up the day, which leads to less cursing, and more happyness. So I put hops in a bag.