There is no just one company that makes blank skateboard gear - they are usually made in China, by several companies, and shipped and sold in bulk. Because of this, it's hard to tell if you are going to get anything well made or not when you buy blank gear. So, I would recommend avoiding them, but there are times that you might want to buy blank stuff. So, here are a couple of things to look for:
Blank Decks- You have to be careful when buying blank decks, as some companies use cheap, softer wood that won't have good pop, and definitely won't last. Make sure the deck is made from 7 ply rock hard maple.
According to Marc from Marcs Board Shop, he gets his blank decks from TGM Skateboards. They sell 100% Rock Hard Canadian Maple Moose Decks, and Marc says he's sold piles of these and that people have been pretty happy with them. It can be tough to know if you are getting quality, though. Ask the owner of the shop you are buying the blank deck from, and make sure it is made of good wood. If it is, it should be OK, though don't expect it to last as long as a pro grade skate deck. But, if you aren't too aggressive in your skating, it might work out OK for you.
I want to point out here that blank decks and shop decks are NOT necessarily the same thing. Sometimes they are, though - so ask your shop and find out if you want a shop deck.
Blank Wheels- There's no real way to make sure of the quality of the eurethane in the wheels before you buy them - you can ask at the shop you are looking to buy them from, but there's a good chance they won't even know. If you can get them cored, that will help.
Blank Trucks- There aren't really honestly blank trucks out there, but there are low end cheap skateboard trucks on the market that fill the same role. Industrial would be one of these brands.
Blank Bearings- These are everywhere. Just make sure they are ABEC rated, around 5 or 3 or so depending on your skateboarding style. Most of the time you can get a cheaper good quality bearing set like Bones Reds for only a little more money, but that isn't necessarily true everywhere.
So, if you feel convicted about it, or if you have the money and want something quality, by all means get pro grade skate gear instead of blank equipment. But, if you are strapped for cash, or you just don't want to support pro skating, then blanks aren't a bad idea. But, you get what you pay for, and if you re serious about your skateboarding you will probably want to upgrade.