Not really necessary, no.
It would be good if there was a VOIP company that could offer cheap rates on local calls in the DR, right now you can get good rates to the US or wherever, because of course the VOIP company is based there, but if you use that same service to call a local number of course it's like long distance. If a company could come in and work out a way to do local VOIP on a low, flat rate basis WITH good rates to the US and Canada they could probably clean up.
My guess is Verizon would be unhappy about this, and since they are the biggest local phone company AND ISP they would make it an uphill battle.