I don't get it much, although I can understand why it would be annoying. I do get excited if someone knows what mine are, instead of telling their friends confidently "Look at that, must be some sort of Lassie Greyhound. Or Staghound." Or "Those are Afghans you know." Insert eye rolling here.
Same as the "You could put a saddle on it!" sort of comments. Oh yes, hilarious. I've never heard that one before...
I do much prefer when people are just curious and ask, instead of making the dorky jokes, or trying to sound all authoritative.
My mum used to have a blue and white working bred Kelpie - he did have a little Border collie way back so was "Irish Marked" but built kelpie style. No one believed he was mostly kelpie, and blue was pretty unknown in BC circles at that time as well! At least I suppose he got extra attention!!