Does not compute.
I have used PDANet on a 3G and 4 very infrequently over the years on an AT&T unlimited data plan and have never been notified. Does PDANet hide tethering better, or have I just dodged a bullet?
Does anyone know for sure how AT&T detects it?
Is there a tethering app(s) that has never gotten the notice?
You have just dodged the bullet. Like we have stated, usage spikes are certain to get you noticed. Sporadic or infrequent usage is ok. Its just using it as a (or similar to) home connection will definitely get you noticed.