I agree in some cases, but simple words like Nani? Ano? Arigatou etc. are 
pretty easy to understand. And even the more difficult ones are also if used
in a good way. For example, Kun-chan's lemon series uses a LOT of Japanese words
to describe *ahem* yet it is pretty obvious what they mean. AND, as a bonus, you
learn a little Japanese.

I agree with Misa-chan.  I had no idea what words other than "arigatou 
(sp?)", "sayonara", and "ohayo" meant.  Reading fanfics helped increase 
the extent of my Japanese.  In many fanfics, it isn't hard to decipher 
what certain phrases mean from the context it's used in.  It took some 
time for me to figure out some phrases such as "gomen-nasai (sp?)"--please 
excuse my horrible spelling--but I think that adds to the fun of reading 
the 'fic (yes, I have a sick sense of fun, but after two years at a 
service academy, you learn to enjoy the little things :) ).  I do agree 
that too much can distract the reader, but I guess I'm fortunate that I 
haven't run into many of those.  Just my two coppers worth.  Take care!

Respectfully,
MIDN Mac O. Quidem
United States Naval Academy
"an okonomiyaki addict, and proud of it!"