Depends on what you constitute as sharing.
If sharing means buying a CD- buring three of four copies for your buddies, then no, it should not be legal. One thing I find in the argument against the artists and labels that are taking action is that it's ok to make copies and share files because they are rich.
If you mean downloading and sharing files that are free. Go for it.
Music is a product. Inside those record companies are many people like you and me. They sweep floors. Do accounting. Make sales calls etc. These people depend on that "product" getting distributed at a profit. But the companies make too much money you say? So what. They have the right, as do you.
My friend is an artist, a darn good one.
http://www.godardgallery.com/birch.htm (check him out)
He painstakingly works and reworks a piece until it is complete. These can take weeks. This is how he pays for his life. He then sells them for thousands of dollars, after broker fee's (if involved) and the gallery take it's cut he is left with considerably less. Let's say I decide to buy one (which I have, deeply discounted buddy price though). I then buy a spanky new photo copier and make really high quality copies for all my friends to hang on thier walls. Are they going to buy a Nathan Birch, likely not, they already have one. That is not right.