The Myth of the Online Dictionary:
That's Not a Word!:
Everything in the dictionary-online is still seen through the lens of print, and what print needs. The web is an afterthought. Even the wiki-style dictionaries (which I am all in favor of, and I'm on the advisory board of the Wikimedia Foundation) are largely based on print ideals of organization and inclusion. (Even Wiktionary wants words to be at least a year old before they are included in the project.)
A true Online Dictionary would be created with the web in mind. And it might not look the way we think a dictionary "should" look at all!
The ruler most people use to measure a word's word-ness is The Dictionary. Not any specific dictionary -- for most people, if a word is in any standard-looking dictionary, that's good enough. (The Dictionary is a stand in for "Any Dictionary I Happen To Have.")
But as a lexicographer, as someone who has seen how the word sausage is made, I think that assessing a word's fitness for use by whether or not it is in The Dictionary is much too limiting. We've already seen that lexicographers can't possibly register, much less describe, all the words that are used in English; how then, knowing that, can you still cleave to the idea that the words that are in The Dictionary are good to use, and the ones that aren't, aren't?