I keep hearing about them once and a while but I never see any sites that take them and I dont really understand what purpose they play. Are they just easier to mine?

Is it anonymous? Well, depends on who you're talkin bout. Big brother can do pretty much anything they want and nothing will save you from that. 

I backup my wallet, use 2 stem authent and encrypt but how dangerous are Macs in general to these attacks?

The government absolutely hates the Bitcoin. Its an anonymous way for people to send money thats hard for the government to even seize. After the fall of the Silk Road, i believe 60,000 BC's were confiscated, and the U.S couldnt even collect on half. Not only that, but the Bitcoin is a competing Fiat currency (meaning its value is derived from faith)  just like the dollar, only tradable worldwide and creating a huge exchange worth billions. One of the biggest problems BC allow is for easy laundering of huge amounts of cash, with privacy that really helps drug dealers hide that pile of money under the mattress into something digital, tradable, and non stealable. That being said, the BC was primarily developed in Europe and most of the hardware/ currency is stored there. Given time and the growing popularity given by the silk road bust, I think the U.S must eventually integrate the BC system.

http://cdn17.castfire.com/video/305/2242/8032/627455/cbsnews...

The troubling bit can be found at ~7:00 in the video.

Interviewer: "Are you worried about the government shutting you down?"
Jeff Garzik: "We're actually working with the government to register Bitcoin exchanges as MSB's, or Money Service Businesses; To make sure that the long arm of the government can indeed reach Bitcoin..."
Jeff Garzik: "The only way Bitcoins are going to be successful is working with regulation and with the government..."

Yes we are guna have problems.
BC will never replace gold, as with any Fiat system. WIth the falling value of the dollar... BC's do seem kinda appealing.

my 2cents

Victorinox