In several astronomy-related Yahoo groups I dabble in, the subject of rebar has come up over and over agian. Some insist on it, some don't. I think it's application-specific, though many of my esteemed online associates disagree. The pier is already encased in 3/4 inch polymer tubing ... the concrete is not going anywhere, it seems silly to me to reinforce it with rebar, especially if the concrete is mixed and poured correctly. But yes, I did throw in some rebar just to keep the pier-hippies happy.