Also, go on Ebay and look for Berenstein bears. There are aucitions for the books, but the sellers list them as "Berenstein" but the pictures of the books is "Berenstain". I'd post picture, but you could aruge it's shopped, so look yourself. My theory is the people posting the auction believe it's Berenstein.
I went to a BBQ today after reading this post, thinking my noodle was cooked. I asked the hostess, without pronouncing the name. She said "Berenstein". I later asked a middle school teacher what the name of the series of books was, she said "Berenstein".
Researching this fenomonon, there are other tidbits of history that aren't right: the famous guy in China who stood up to the tank in Tianaman square, what do you think happened to him? Then go look it up.