7 OS devices: data security. BIS and BES services: differences of them, a level of security.

Hello,

I'm not a person, which is highly knowledges in IT.
Reading this article, I found, that BlackBerry using with BIS (we're talking about 7 OS) is absolutely unsafe and outgoing data is not encrypted ! As I understood, a full data protection and encryption is only using BES (BlackBerry Enterprise Server), when only when BlackBerry is communicating with BlackBerry can encrypt the data. Am I correct ?

So, there is a few questions:

1. Is BIS still safe or BIS safety is just a myth ?
2. When using BIS, data transmission is going with your mobile network carrier (operator) server or using BIS the data is going to RIM's (BlackBerry) servers ? - It's the main question.
3. Are BBM messages encrypted using BIS ?
4. If a full data protection is only using BES, how does it cost ?

Thank you for replies.