They aren't meant to be hard to get, or even to be obtainable.
The reasons why no one should be upset about these are at least twofold.
1. They don't do anything
In SC2, I have 3 feats of strength.
I finished in diamond in solo. I finished in diamond in team, and I bought the collector's edition. None of these three feats impacted my ability to play SC2 at all.
I will not be getting the beta feat of strength. No will I get the presumptive collector's edition feat of strength. (Everywhere around me sold out of collector's editions weeks ago)
I don't anticipate my lack of either of these feats of strength impacting my ability to play Diablo 3 at all. Furthermore, I doubt Blizzard will allow these feats of strength to have any in game significance, beyond a possible sigil variant.
These are simply Blizzard's way of acknowledging beta testers.
2. Why should it bother you?
As I mentioned above, in SC2 I have a feat of strength given to me because I have the SC2 CE. Why should this have bothered anyone? It didn't remove anything from anyone's version of SC2. All it did was point out that I had bought the SC2 collector's edition.
Similarly, if Blizzard decided to give feats of strength to beta testers, why should anyone be upset? It doesn't remove any aspect of the game for you. If Blizzard decided to give these beta testers very cool-looking aesthetic artifacts, or worse, in game items which impact gameplay, then you could have a right to be upset. As it stands, there really is no reason to be bothered.
At any rate, I regret if I added more fuel to the fire.