It makes me cringe...
+1000000
Sometimes I ask a sale person a question I already know the answer to in order to see if they know what they are talking about, bullguanoting, or at least willing to admit they don't know (which I honestly don't mind that much, no one knows everything).
Feigning ignorance is trick I learned from my dad, as he would say: "If you let someone talk, they'll tell you exactly how stupid they are."
ANY big box store is 90% know-nothing bullguanoters, and a decent percentage of smaller shops have their share, but usually to a lesser extent. No offense to anyone here.