Besides pointing to the fact that it is a rule, what is the safety issue of using a phone before pushback? I can't really see the plane crashing or the crew having navigation problems during that time. So what is the reasoning behind this rule?
I never take phone calls while on the plane, but I do keep my Blackberry on until pushback. After all, the time between boarding and pushback often takes a while, so why not use the time to read/write e-mails? I am not sure whether this is allowed or not since the safety briefing is usually only made when the plane is moving, and it is only mentioned then that phones should be switched off.