Interesting discussion...we still have the land line, but with caller ID, we let it go to voice mail if we don't recognize the number or name. As for cell phones, well, our adult children, my husband, and I have them with us 24 x7. We don't get bothered as our phones have caller ID, so it's the same process in "answering" as with the land line.
My husband and I both have "smart phones". They're quite handy in a disaster, such as an earthquake. Last year, when the Napa, CA, earthquake happened at 4:15 AM, we felt it at our house, 75 miles away. No damage, etc., at our house. Knowing, however, the media would make it out to be tantamount to the 1906 EQ, I used my smart phone to access Face Book, making note that we were OK / no damage. Then, I went back to sleep. My cousin, who lives in the Midwest, commented later that FB was the first place she checked for our status as she knew I would use my phone for the "reporting in" message.
In the case of a natural disaster or catastrophe, if you have a cell phone, DO NOT TRY TO CALL ANYONE. Send a text message, instead. Texts use very little bandwith; saving battery and internet resource.
If you live in an area prone to disasters, set up a far away contact, preferably someone well out of the area / region. Provide that contact's info to relatives and friends, etc., letting them know you will reach your contact and that person is their point of contact for exchaning info. and status about you and them. If / when the disaster occurs, text (or phone -- you can make one call) your contact, letting them know your status. It's much easier to make one call or send one text than answering the phone while you're dealing with chaos and uncertainty.
This "remote contact" info is endorsed enthusiastically by all emergency services personnel. I've used it and it works.