Why would "Doberman" not be in a scrabble dictionary?
It's a proper noun... maybe those online dictionaries are not the highest quality? The full name of the dog is the Dobermann pinscher, the name itself is that of Ludwig Dobermann, a nineteenth century German dog breeder. 'Pinscher' means 'terrier', and can apparently be spelt without a capital, check yer Scrabble dictionary to see if it's in.
Why does the Official Scrabble Dictionary have an eight-letter limit?
Even if a word like Basketball isn't in the Scrabble Dictionary, that doesn't mean it's excluded. From the official tournament rules at http://www.scrabble-assoc.com/build/rules/rules2.html :
"For words of more than nine letters, the OWL [Official Word List, a list based off of the Scrabble Dictionary] is consulted first. If a longer word (more than nine letters) is not listed in the OWL, to be judged acceptable it must appear in the Long List (LL). The Long List was compiled from Merriam-Webster's Collegiate Dictionary, 10th edition."
The reason that the dictionary stops at 8 letters is because the vast majority of words played in scrabble are 8 letters or shorter, as it's difficult to build off of two letters at once in the same direction. If you want to check a word longer than 8 letters, just look it up in some other dictionary and see if it follows normal Scrabble rules.
Do you think the editors of the Scrabble dictionary make up words?
Not really! The words are generally updated keeping in mind current trends and words that are used more often. Although they do give partial preference to Scabble players by adding new words like Za, Qi etc. which I feel is justified. Maybe it takes the skill out of Scrabble, some may argue, but as it is equal for both players, they both have a chance to get some nice points!
And if you keep yourself up-to-date with the dictionaries you will see that the changes are very logical and you can anticipate them too. I for myself, do read the word list everyday. If you want, check out more info on Scrabble dictionaries at http://www.scrabulous.com/scrabble_dictionary.php
You can find both SOWPODS and TWL at Scrabulous.
Merriam-Webster publishes the official scrabble players' dictionary. It's cheap (under $10) and easy to consult. I wouldn't recommend using it as a day-to-day dictionary, but for the specific purpose it's the best. Pick it up on Amazon if you can't find it locally.
It's also endorsed by the National Scrabble Association, so if you're ever interested in playing competitively you will want to have this.