I 100% recommend putting tyre armour on your springs. The extra weight is neglegable... especially if you put them on before your first session since you'll have nothing to compare it to. =) ...and they're really not that heavy anyway. I would assume that someone who couldn't handle that little added tyre weight would also have to bock naked to save on the added weight of clothing. =/
The people that put shoes... like actual SHOES on their bocks, is that not dangerous? Seems like a tripping hazard to me for sure.
I also 100% recommend putting shoes on your bocks. But make sure they're the right shoes. It should be obvious what I mean when I say that, but I'll give you the two main factors anyway. Go to multiple shoe shops (with your bocks!) and try lots of different shoes to find the perfect pair.
1. GRIP - There are literally millions of different shoes. It's a bit crazy to say that none of them would be as grippy as tyre socks (sorry DK). I know mountain bike tyres are grippy but I've never seen a bike climb vertically up a rock face. Climbing shoes do... I'm not suggesting you put expensive climbing shoes on your bocks, I'm just making a point. =) Try the shoes on your feet to test grip. Try quick turns and changes in direction, and if you can, try hanging on something with your feet against the wall (known as arm-jump position in Parkour). This might seem a bit weird in a shop... but I do it whenever I buy shoes! lol. As a traceur, the grip on my shoes is very important.
2. FIT - This is crucial! You're right, if you get the fit wrong they could be a trip hazzard. So put the shoe on your bock to check it fits. The shoe should be slender and the hoof should go right to the end. The tread of the shoe should round upwards over the toe so you have grip when running. The shoe size (as in length) is relatively unimportant. I originally tried as small a shoe as I could find. But in the end, it was the width and shape at the toe end that was the important part.
The shoes I found fit so securely on the hoof I wouldn't need to worry about it slipping whilst bocking. But to be absolutely confident with them, I also use a pull-tight strap on each shoe. You could use a cable tidy.
I recommend searching for the best shoes yourself. But I use ALS men's King Surf shoes. They were £20 from Blacks. I found a size 8 or 9 fit the best. The grip is fantastic and lasts forever. And the upper is kind of elastic so it perfectly accomodates and moulds to the shape of the hoof. A final tip is to put the piece of card (that comes in the shoe) ontop of the bock, then slip an actual sock over that. This helps you ease the bock into the shoe without the bolts catching on anything.
The tread should last a LOT longer than with tyre socks. Some people manage to kill them in 10 hours! And as an added bonus, shoes look awesome when you wear bock pants! ^_^ (though slightly stupid the rest of the time! lol).
I think tyre socks are kind of out dated now anyway. If you don't want shoes. I think Jason's hoofies are the way of the future. ^_^
EDIT:
Oh wow, they're actually only £10 at the moment. =) I got them in black.
http://www.blacks.co.uk/footwear/men/product/082365.html