Beer and Medicine
When I lived in San Diego, at one point I got the flu. I found out that the local farmacist was three isles of different kinds of medicine in a supermarket. So I tried to locate this anti-flu product called Contact, which I couldn't since it was indexed under K, naturally. Leaving the store I found a type of weiss beer that I really liked so I grabbed a sixpack of that. I had to leave that six-pack because I did not have my passport with me... Couldn't convince them I was 30... but I left with sedatives strong enough to kill a horse.
In another supermarket I had to show my passport every time I bought beer - even though it was the same person behind the cash register. She knew who I was, but since supermakets and bars get fined around $10,000 and loose their liquor license and people loose their jobs, I had to be checked throughout my whole stay.
Later on I found a more liberal supermarket where I could be bottles of whisky and beer and never shoved them any kind of ID... Wierd coutry!
Several times people tried to guess my age. The lowest was 23 and highest was 27. I guess people in California just grow older by the looks faster
Getting a driver's license
Tourists can use their European license during their three months stay, sure, no big deal. Being a resident in California you need to have a driver's license, since you can only use your license the first 10 days! Getting the actual card takes 8 months... I was there for 7.
Getting your car stolen
I had my rented car (read: an old wreck) stolen at some point and it was found one week later just south of the border, completely stripped. I had to file the theft to the local police. They never asked for my driver's license, and they never reported back to me.