I thought VPN is supposed to be secured

(emphasis mine)

The only constant in security is that it can be royally fucked up a hundred ways from Sunday, and there's only one right way to do it. Which would be to hire a very expensive team of security experts and engineers, and trust no 3rd-party software whatsoever. For obvious reasons, very few companies operate this way...

would you trust communication which involves your company's most sensitive data over VPN?

Your choices are (a) trust a VPN, or (b) don't communicate over the internet. Since (b) is is clearly not acceptable in this day and age, you trust a VPN. Though apparently, not a Juniper Networks VPN.

Implication: would you trust communication which involves your company's most sensitive data over VPN?

No. The Snowden documents seem to indicate that VPN is not a problem for the NSA. Even though VPN is secure theoretically, there's a few points of attack, such as everyone using a few seed numbers, that makes it probably not safe if you're trying to hide from the government.

If you're using VPN to hide from your competitors, and your competitors don't really have the pull to use governmental espionage to read your secrets, then you're probably safe.

Relevant XKCD:

https://xkcd.com/538/