You should always keep up with Flash updates, because Flash can have security vulnerabilities that can compromise your machine. (Admittedly, there has yet to be any malware that uses Flash to install on a Mac, but there's a first time for everything.)
However, the only way you should ever update Flash is by downloading the latest version directly from Adobe's site:
There has been malware that pretends to be an Adobe Flash installer. That is, in fact, where the infamous Flashback started out before switching tactics this year. So never trust any site or e-mail that tells you that you need to update and provides a link! Get it directly from Adobe instead.