12:08 p.m. on August 21, 2012 (EDT)
The biggest thing here is that nothing lasts forever. Different terrain will have alot to do with how long some items last.
Tent stakes being one of those items.
I have the GroundHogs. Then again I have a ton of other stakes as well.
Now with that being said I have broken many a stake here in Pa over the years. Pa is notoriously rocky. I have on more than one occasion had to move tent location due to the fact that I could not get a single stake in the ground(thought I was on bedrock.)
Stakes are not indestructible by any means.
Just like all gear it is very wise to check them prior to any trip for deformities, nicks, deep gouges, scrapes, so on and so forth.
All of the above can have a significant impact on the strength of a stake regardless of how awesome they are.
To me this is somewhat similar to aluminum tent poles. It is wise(and recommended) to inspect them for scratches before a trip because dependent upon how deep a scratch in a pole actually is can greatly reduce the strength of the pole and result in a crack once stress is placed on the pole itself.
Lets face it...
Aluminum is not some indestructible wonder metal. Over time stakes do need replaced.
This is somewhat dependent upon frequency of use as well as areas of use. If I only utilized mine 1 or 2x per year the need for replacements would be much less compared to how often I actually do need to replace them.
I am out quite a bit.
Keep in mind different designs in stakes excel in different conditions, ground types, etc.
Mine are the same as the ones in Franco's photo.

tiredofwinter, did you replace the line on yours?
Another thing I would like to point out...
If you look closely at the photo below(tiredofwinter's) you will notice that there is a substantial amount of deformity at the area of the break.

This leads me to believe that either there was a pre-existing problem with the stake itself(ie crack) or it ran into trouble when it was placed in the ground(unseen rock, etc.)
Deformities like this just don't "happen" on their own.
The GroundHog is actually a pretty good stake(imo.)
At the same time it is no different than any other piece of gear in the regards that all gear has limitations.