Originally Posted by apecush
The appearance of those arms doesn't instill a lot of confidence - they are very thin stamped steel (though probably fairly high-strength). Given the stiffness of the rest of the arms (solid aluminum) it isn't surprising that they are deforming. They are carried over directly from other 3-series cars where the suspension linkage is likely quite a bit more compliant, not to mention higher profile tires - perhaps they are there to protect a weakness of the subframe.
Like I said before, I'm pretty sure this issue is more widespread than most believe, since a very small percentage of us actually inspect the suspension components on our cars closely enough to see the damage shown in the pictures.
Like others have said, it is the weak link because it is designed to be that way. The way it fails is actually a safety feature which keeps you from losing control of the car. The OPs situation definitely doesn't look normal and does appear to be caused by someone prying on it which I have heard is common for some inexperienced installers to do when installing springs.