It looks positively ridiculous, not sexy.
Even I have been guilty of striking this pose...but for good reason. We were in Paris at Châtelet - Les Halles Place Igor Stravinski and it was only natural to do the duck lips in front of the fountain.
Aside from posing with this specific art piece, there really is nothing natural about the pout. More than likely, people are laughing at you and not with you when they see your puckered up photos.
The only time you should have duck lips in your pics is when you are one of these two: