If you have a cable modem (Comcast or whoever) and a cell phone, you don't need a phone line for anything.
SD
When we went from dial up to DSL last year we went Verizon because their plan was no more expensive than our dial up. At the time, Comcast didn't have Internet in our area. Now they do. Plus, their plan is still more expensive than Verison's DSL, but dropping a land line, it's something to consider when our Verizon contract comes up in a few months. The difference will mostly be the difference in cost between our current 400 minutes a month and 'unlimited' calling. At present we don't even come close to using up those 400 minutes.
My brother was forced to get a landline; the bank would not approve his mortgage application with "only" a cell phone as a contact point.