It's hard to get the perfect tone of voice, but it's very easy to get the wrong one. Mostly companies get the business buzzword version (see my post: Buzzwords from hell), but occasionally, they get it very badly wrong.
For example, Michael Kinsley has written an article in Slate ('CryptoKids at war') about the recruitment pages for lawyers on the CIA website (and, by extension, exposing the legal doublethink that is going on there). Some of the writing on the Office of General Counsel's site is priceless. For example:
If the theme music from Mission Impossible runs through your head, or you get the urge to order a martini "shaken, not stirred," at the mention of the letters "CIA," then visiting the CIA’s Web page won’t disappoint.
Compare and contrast the British MI6 recruitment website which is factual, understated and, as a result, much more believable and effective.
SIS operates around the globe to collect secret intelligence in support of British government policy. The work of the Service helps the government respond to threats to UK interests such as regional instability, terrorism and weapons proliferation...
Basically, it's Felix Lighter and James Bond all over again.