I had a scary experience last weekend trying to watch UFC without paying for the full PPV. My friend recommended a site called MMAShare, went there and paypal'd $11 for the entire main card. Clicked a link I thought would take me to the fights, it asked me to allow popups, which I stupidly agreed to thinking maybe the fights would popup in a window, then all of a sudden I was overwhelmed with anti-virus popups claiming I had been infected. Yikes! Luckily I recognized that all they were were popups and not an actual infection....yet. I closed down the browser, cleared my cache, deleted cookies and history, and ran my AV software for safe measure. Turns out the popups were bullshit and fortunately I didn't click on any of them or they could have potentially infected my computer. Watched the fights although without sound because the unmute button was a link, not on the video itself.
Lesson: Don't allow popups on unknown sites and watch what you click you shit pirate.