Pop rivets can fail pretty easily too if they are subjected to a lot of torque as in a rod holder.

I've used these for years with no complaints whatsoever and they will probably outlast me and my tripping career:

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Available from quite a few retailers online and perhaps locally as well, depending on where you live.

What I like about them is that the top part of the rod holder comes off quickly and easily at portages and can be reversed to face downwards and thus out of the way for portaging.  Takes about 15 seconds to do it.  The main clamp stays on the canoe from the moment the canoe comes off the car until the moment it goes back on the car. 

The rod holder itself is very adjustable so you can set your rod high or low, swept forwards or back as far as you want.  I have mine set so that I can paddle easily on both sides with no interference and grabbing the rod out of the holder is quick and easy.  The setup of the holder is such that the stress on the rod is on the cork both forward and aft of the reel, not on the graphite/whatever rod blank which can get stressed and weakened by rod holders that rely on gripping the rod blank.