Why am i being ignored?

i went to camp wih a guy summer 2010 and we became very good friends, and even alittlenmorethen tha and we txted all the time but. then on the lastday of camp he started ignoring me! he still never answers any of my txts! (not being stalkerish or clingy, i just txted "hey whats up?" a few times. does anyone know why this is happening????