Well, let's level set. What level of familiarity are we talking about here?
If you don't know what the company logo looks like, you shouldn't own that company. I can't draw a Coca Cola logo but I know sort of what it looks like. I definitely recognize it when I see it.
If you can't name several products sold by that company (assuming they sell products), you should not own that company. I've been inside Walmart and I've seen what they sell, so I understand this part about Walmart.
If you don't know how large the company is or what percentage their market share is (ballpark), you should not own that company. I know almost every desktop computer has an Intel processor and that Intel has the most popular video chipsets, so I know this much about Intel.
Some companies almost act like index funds because of how diverse the company is. I've used HP computers, I have an HP printer, I used an HP gas chromatograph in university, and Best Buy has HP graphing calculators. Companies like GE and Philips sell so many things that they don't really go down unless the entire market goes down. GE's price closely follows the market; a steady $35 until early 2008, bottom hit $7 in March 2009, current price is $18 and going back up. Within a couple years it should probably be right back where it was, somewhere around $30.
Why do people buy lottery tickets and go to the track?
Mental illness? If I'm not mistaken, dopamine seems to be very strongly correlated with risky behavior, downplaying the significance of what is going on (why this is a bad idea), and being overly optimistic of what will happen as a result of doing something. People high on caffeine are a little too optimistic sometimes; I know I often set very optimistic goals when I drink coffee. People who take methamphetamine are known to be extremely impulsive and often engage in risky behavior such as unprotected sex with random people.
Here's an interesting one:
Miraprex, a medication for parkinsons disease. Parkinsons is when you lack dopamine. The side effects of this drug are exactly what one would expect from a drug that increases dopamine activity. Compulsive gambling (ie going to the track and then buying lottery tickets), insane shopping, and hypersexuality.