I think it is a question of credibility. It's the kind of blunder that drags me out of the episode and reminds me of the fact that this is a show made by, uh.... people who are not European.
That's nothing in comparison of certain LEXX episodes with a map of Europe with very odd boundaries: http://littlelexx.net/phpBB3/viewtop...p=10066#p10066
Garbage in, garbage out. Data only knows what the databanks tell him. If the databanks are in error, so he will be, too.
I think, a federation ship's data base size would be comparable to the entire internet of today. Thinking of that, Data might be a victim of Wikipedia sabotage.