I'm pretty careful and I found out that I'd had a 'double-posting' of my own the other day. XD; Server hiccups happen, but in general, yes - other than the weird hiccups, it is harder to have a double-post. XD
-nods- It still happens though, as it just happened to me. I sent and when I returned to the tab and it was 'done loading' so I thought it hadn't sent so I sent it again and found I had posted the same post. It wasn't a real double post as there was a post between the posts but it was still the same message.
It's less likely but it still happens from time to time.