People also don't appreaciate the prospesct of 4 horns in a crash either. But back to the question at hand, a tri bike should also have more meat on the frame around the bottom bracket and the backstays will generally be beefier both in design toward better power transfer. Look at the back triangle on this bike
http://www.fahrrad.de/images/k-factor_1024x768.jpg compared to this bike
http://www.company7.com/colnago/grap...LX%202006L.jpg