I agree, I had a wyeast pack freeze in shipping from an online HBS. I let it thaw, smacked it and let it sit out for a bit and it never really expanded. I made a 1qt starter to see if it came back to life. It had a little action in it, but never really took off on the fermentation. I was up against a time crunch and didn't trust what appeared to me as a weak starter. I got new yeast, pitched it and threw in the starter for good measure. Been 5 days in the primary now, started bubbling really well in first 24 hours, kicked off nicely.
For me it was better safe than sorry, a 45 min round trip to the LBHS and $6 for a new smackpack.