I'm inferring from comments here that companions can be used as pack mules. Normally I detest someone following me around, especially since I like to scale mountains as shortcuts. Someone that can store all the loot from dungeons would be a huge assist, and the first guy that followed me was fairly useful with a bow.
If they die, is it permanent or do they magically resurrect? **heads for the wiki**
A couple of days ago I was scaling a random mountain in search of random loot, and a dragon attacked me just as I found some random lootable area. Everything was going according to script, but halfway through it flew up the mountain and didn't come back. I heard it blasting something and didn't want some NPC poaching my kill, and made my tedious way up the mountain. It took ages to find a path to climb up, and there's the dragon blasting away at something.
When I finally reached the peak, I didn't see anything around and I finally got the dragon's undivided attention. It took a fair amount of my health before I finally killed it--I was extremely low on potions at the time--and immediately after it died a couple of...
...appeared out of nowhere and very nearly took me out. First I'd seen of them and they were tough bastards. After all was said and done, I looked around and found three more dead ones scattered around the peak.
Too bad dragons don't like to follow you or they'd be easily weaponized.