Idle in transaction - Explination ..

Where I work I'm in charge of more then a few PostgreSQL databases.

I understand why idle in transaction is bad, however I have some
developers who I'm having a real difficult time fully explaining to them
why its bad.

Oh, and by bad I mean they have transactions that are sitting idle for
6+ hours at a time.

Mainly because they don't speak very good English, and my words like
MVCC and VACUUM have them tilting their heads wondering what language
I'm speaking.

I've tried searching the mailing lists for a good explanation, but
haven't really found one thats easy to translate.

They are Japanese, but I don't speak Japanese, so finding any resource
in Japanese that explains it is beyond my ability.

Would anyone happen to have a simple explanation, or a page online thats
written in Japanese that I can pass off that might explain why this is bad?

Is there a Wiki somewhere that says "101 ways to cause your DBA an
aneurysm" that covers things like this? :)

Weslee