After a lifetime of pulling trailers I've never had a bad experience...touch wood...but as someone else mentioned, preventitive maintanence goes a long ways. Look after your trailer... (and truck)... and it'll look after you.
One thing I always do is hook up the trailer and do the walk around myself, that way I know it's done right, but one time I let someone else do it and it nearly cost me an accident. I had some work done on my boat and when I went to get it I backed up to the trailer and while I was doing something in the truck the other guy hooked up the trailer & lights. I left and was driving down a country road and when I put the brakes on for a stop sign, the trailer jumped off the ball cause the other guy hadn't locked the hitch down properly.
ALWAYS do it yourself and be sure.
And for what it's worth, I just upgraded from a single axle trailer to a tandem and it makes all the difference in the world when hauling the boat down the highway.