Blackberry Cases

Why does Blackberry have the magnetic cases and what does this do to one's BB phone when put inside or taken outside of the case? I have had 3 BBerry's now and never used the magnetic case, opting for a body glove instead. With this new BOLD 9930, the body glove interferes with most of the best parts of the unit, including its feel, which is why I'm considering just using the magnetic case. Please explain the pro's and con's of the magnetic cases if someone is willing...So sorry for a basic, stupid question but I just can't find an answer. Many Thanks....

Magnet makes the BB go into hibernation mode to save the battery.

I use an Otterbox defender series case on my phone. They're expensive, but well worth the money.