Harold, I would never sign a contract that included a clause like that. Whatever field I work in, the best opportunities for career progression are going to be with a competitor. Good grief - where else would I go?

Most organisations have some form of restraint of trade agreement, but there are usually ways around them. I will say though, that, when my current boss thought my ex-boss (who has gone to a competitor) was trying to headhunt me, he got distinctly ruffled about it, so I suspect there might be a clause against him poaching staff - but not against my going to work there, if that makes any sense.