40% of americans don't have landlines.
700,000 landlines a month are being cancelled

I didn't realize the number was that high. I could live without a land line, but for now with a wife and kids at home, the three of them can share that one land line, she has her cell phone for outside the house and I use my cell phone for most things.
It got to the point where we were having a problem monthly with our land line that I switched to the isp line, if AT&T can't keep a simple pair of wires working its no wonder they can't keep a wireless network working.

I've used Vonage, Packet8, Skype, Optimum Voice (Cablevision), Comcast and a few others. I was actually one of the first 500 users of Vonage. In the early days, the latency (delay) was bad enough to be noticeable, and still the quality can suffer over slow or congested links, but with a good connection, the quality is indistinguishable from a wireline phone. In fact, in many cases the quality was superior.

You can't beat the value of net phones. Unlimited minutes for as little as $10.00/month (let's not talk about "NetJack") and no government surcharges or telco taxes. It's amazing that I can remember paying over $100/month for phone and long distance service not that long ago (but hey, I remember when TV was black-and-white).

Unfortunately, I don't see net phone remaining free from government taxes and surcharges forever. Eventually the government will have to recoup the revenues lost and will start messing with net phone service.

A barrier to totally replacing wireline phone service is the problem of poor penetration of broadband Internet service throughout America. Sure, if you live in a metro or suburban area you're in good shape with multiple options. In outlying suburban areas you might be able to get ADSL or Cable Internet. In rural areas, you're lucky to have any options at all. It's unfortunate that the US rates as one of the lowest of developed nations in terms of high speed Internet access.

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One benefit of phasing-out wireline phone service might be that the government would pay more attention to cell phone carriers. It would be nice if they did more than just auction off radio spectrum to the highest bidder. Force the cell phone companies to stop making up bogus surcharges and fees that add as much as 30% to your advertised monthly service charge. Stop making us pay for incoming calls and texts, as is the case in most other countries. Eliminate the monopoly that some carriers exercise on equipment. Standardize on a single cellular protocol and prohibit carrier-locks on equipment. In a free market there's no reason why cell phones should cost more than $100 or smartphones more than $200. That would also eliminate the excuses for charging high early termination fees. My iPhone clone does almost everything the genuine iPhone does and cost me $70 without a contract.
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I dumped my landline years ago. Knowing that the primary disasters we are likely to face in my AO will all take out landline infrastructure I opted for cellular coverage. Cell companies can get portable cell towers up in relatively short time.
In the California wildfires, Verizon claims it never lost any coverage areas because they had the cell trucks out there covering the area. Those of you in that area can attest to the veracity of that claim.
VOIP is probably safer and more secure for the home user than standard landline. Anyone with an induction coil can pick up wire communications. VOIP would provide more security than that. Not that i would entrust any really covert communication to any communication device commercially available...