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right now, there's a pretty popular windows virus that watches your clipboard, and every time it sees a bitcoin address there, it generates one with the same first-few and last few letters, then replaces it in your clipboard, so when you paste the btc address youre trying to send money to, instead you paste on that looks the same on quick check but is actually controlled by the bad guy.

We have iMacs, that's crazy, are there any viruses like that that can infect macs? ...this whole thread and post is the kind of news I need!

It won't reduce the risk too much. The real issue is that, since there isn't a mediary like Visa, you won't have a recourse for fraud. So, if someone steals the money, you're screwed. It's like cash, except potentially way more exposed since there aren't physical and geographical constraints to the usage.