Zero, there are some local codes that require a gas line to be grounded to the whole house system or to be grounded independently. Also, some allow additional bonding to the gas line. Gas lines need to be grounded just as much as other things especially in homes where the gas and electrical tie in to one appliance (furnace, oven, dryer etc). The potential of both systems must be kept in balance.
Also gas moving through the lines can create a build up and that must be dealt with.
Not saying it is the best thing to do, but I know for a fact my own house, the whole grouding system is one. Gas, to water, to electrical ground rods. Some areas alllow it and some require it. Some prohibit it. Either way, all the grounds should be done by professionals from each utility and they also should make sure the line is marked as to where and where not to insert new bonding straps so as not to break the main ground run too many times. Also, the gas utility itself might have it's own rules that can supercede local codes. If the codes allow it, the utility can say no.
Honestly, I don't know if I would want a contracted sat, cable, or phone installer tieing into any ground on my gas line.