Besides the big boys like Total Wine and Bevmo, there are smaller places around the OC and Los Angeles area that people will sometimes stumble upon which stock some hard to get beers.
The "Liquorette" has that classic liquor store front in a sleepy little city of Walnut, just outside O.C. The man you want to talk to is named, "Joe." He knows his beers and prides himself in keeping the good ones cold and hidden in the back. If you want more than one Pliny ($5.99), he'll have it in the back more than likely, so just ask. A very nice selection of microbrews as well as some commercial favorites.
I finally went there yesterday after a friend highly recommended it. I am also "friends" with them on FB and get constant updates about new shipment. Last week, the shipment of Stone's cherry stout was limited to 2 bottles per person and sold out in 2 days. I picked up the La Fin Du Monde for $6.99 and the Maharaja for $7.99.
Hi Time Wine Cellars (Costa Mesa)
Lone Hill Liquor (Glendora)
Hi Time has a wider selection, but I find Lone Hill occasionally has some stuff that can't really be found elsewhere in CA. The owner [Sam] was carrying some Dogfish Head before they were officially distributing here, and I've seen Three Floyds in the cooler too.
O'Shea Brewing down by me in Laguna Niguel often has some hard-to-find beers, but they certainly have no qualms about pricing at the very top of the market to ration supply rather than pricing at MSRP. Years ago I bought a 22oz of the heavily-hyped Firestone 10th anniversary from them for $35 (and it was *amazing*), and a few weeks later as it was getting even more rare I saw it on the shelf for $55. Of course, if it had been priced at $10 it wouldn't still be on the shelf, so I can't begrudge them for rationing supply through price. But you can expect to pay a little more for what you find there.
You just never know. There's a place in signal hill I went to by chance, and wish I could remember where. Dingy ghetto little store. I wasn't even checking the beer out, I was getting a soda. Top to bottom, just one door in the wall fridge, maybe 40 different 22s. All my specific favorites were there, and the rest were ones I wanted to try. My head was on other things, and i let it slip away.