Is there a security risk to adding "ActiveX controls"?

I keep getting prompted that I should add ActiveX controls to better view videos from time to time. My system keeps giving me to option to add or not. I think I read somewhere not to do it.
Does anybody know the story?

An active-X control is an executable just like any other program that you can download. And just like any other downloaded program, active-X can be used for malicious purposes as well as useful ones.

Many website's active-X will deliever to your computer>> spyware and adware, often by misleading the visitor into downloading an active-X control that the website claims is necessary for the site to "work".

Only let active-X be downloaded from reputable websites that you trust 110% and never allow any active-X control to be downloaded that is not "Signed". Always err on the side of caution when downloading or allowing the use of active-X controls. And always try to use the website first without the active-X. Many times it will "play" just fine!

And never lower your Internet Explorer security settings in the Internet Zone below the default settings to allow an active-X control or download. That is "Medium" for IE-6 and "Medium-High for IE-7. Almost all reputable websites will work fine with the default settings. Doing so is a huge security risk.

Most are safe, however Active-X is the single biggest security flaw in Internet Explorer. If you do not trust the site I would not install the active X control. I highly recommend using Firefox which does not natively support Active-X.