While this is not to suggest that you cannot deal with people online, allow me to explain a phone call I received today.
 In the past couple of months, I have purchasd two balls from people on this site. Let me begin by saying in both cases I do not believe that either were responsible for what happened. I will also not mention their names as I do not wish to harm their reputation by being mentioned in this post.
 Today I received a phone call from my credit card company asking if I had been oversees. I told them not since I had been in the military 5 years ago. The lady asked if I had made any purchases from oversees via the internet....again I answered NO. She asked if I knew of any charges I had made for $xx.xx, $xx.xx,etc. and once again I said...No. I said in fact the only charges I have had on that card were for purchaces mentioned above and one to another pro shop that is REALLY well known to users here, and that was 7-8 months ago.
 The purchase to the latter was made over the phone, as well as the first purchase through a registered user on here who many have dealt with. The latest purchase I went through PAYPAL for the first time. My CC# was never disclosed as far as I know to the dealer. These are the only 3 transactions I have made with this card. Has this ever happened to anyone else? Perhaps with Paypal?
 I am not resposible for these charges, or so they say, however I just wanted to bring this to everyone's attention and hopefully keep this from happening to anyone else as I was lucky.....hopefully.
 The only thing that I am concerned about and this is not an indictment towards anyone, is that the last purchase came with different weight and top weight than he said and even wrote down. I had been thinking about dropping a lb. in weight so I said screw it and tried it anyway. The ball is great, but now after this happened, and the difference in specs, and the fact that he and another user had some "misunderstandings" he no longer posts here....as far as I know.
 So keep this in mind and only deal with people you trust. I know it can be easy to trust people when they have something you really want, but patience or dealing with a local may be the best bet for piece of mind.

I agree with Urethane. I have been using paypal for 3 years now, buying a lot of stuff, and also as an ebay seller with almost 2000 feedbacks. I've never had a problem with any transaction not being secure.
I do, however, get worried about emailing a credit card number - if I have to do that, I do it in two or three emails.
If I fax it, I'll send 2 separate faxes.
Paranoid? Probably.
Victim of fraud? Not so far...