IMO with a dipole I would just ground the shield where the coax enters the house.
With a tower it is a bigger concern. My friend has a FM broadcast tower and antennas on his property. It is about 40-50 ft, I'm not sure how high. It has the heliax shield grounded to the tower in several places along it's route down.
How far you want to go with ham antenna grounding depends I suppose on your perception of the potential risk. In some parts of the country it is a far greater threat than in others.
In any case, all lightning grounds on your property should be bonded to the ground for your electrical service.
What makes a good RF ground is different than what makes a good lightning ground.
Pretty good article about lightning protection here;http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget