Wow, nothing you wrote leads me to believe that the guy had any ulterior motives other than friendship. I've found many instances of nice interactions with strangers through ebay and here and even an exercise group on yahoo. In fact, it's kind of refreshing when people are just friendly and neighborly in those "faceless" environments.
Some people are nice.
Oh hey, I worked in a PD and really know about how bad things happen and I'd suggest you look much closer to home for people you know - most people are victimized by people they know and far less by random strangers. Sure, you should be safe and secure, but friendly email exchanges are not anything to worry about in my book.