I've always thought the "tell us what you know about the company" question was basically just fishing for compliments. Might as well say "tell us how great you think we are." It's irrelevant to the majority of employees; so long as the job's interesting and the pay's reasonable, and you're not working with sociopaths, the company could be an international cheese sauce and brass screws manufacturer for the difference it makes.
I ask this in interviews...it's the first question I ask.
The reason I ask is not to test their knowledge really, but to gauge whether they have made the effort to prepare.
An interviewee is selling themselves, and if they can't be bothered to spend an hour or so doing a bit of research and have just turned up...why should I buy?