Wonderful question. Since this is tagged as "Farenheit 451", we can look at it through today's lens as well as Bradbury's. Writers who deal in the future often looking at something they saw in minutia or on a small scale in their own time.
Are we lonely because we haven't real conversation in our society? Real is the key word. Our society often communicates in text messages and emails in which the writer may have put thought, but not writing into its content. Therefore, the message may be lost. Even face to face conversation often loses meaning due to lack of effort. The result of this can certainly be loneliness and feelings of isolation.
What people choose to do with mass media determines the extent it controls our lives. For instance, I hate visiting with one set of relatives because the TV dominates the visit. I have never seen their television in the off position and their watching it continues the entire visit. Therefore, they are to a very real extent isolating themselves from the very people around them.
I like this very philosophical question! I think society is more lonely and we have retreated away from real relationships into more 'virtual' friendships that involve distance. That relationship may be with the characters on television who we follow and sometimes believe to be real, or with some would be friends that we 'collect' on social networks such as Facebook. Of course these are not social networks in the truest sense, because the realtionships are conducted behind the computer screen. In the book Fahrenheit 451 Mildred wishes only for that fourth wall of television so that she can be completely surrounded by the characters she lives for and interacts with. In the past our ancestors lived in smaller communities and social activities were more communal. We are in danger of creating a society that is insular, imaginary and sedatary. Something many people are discussing through the very networks that avoid them meeting other 'real' people face to face!
I agree that through text messaging, emails, social network sites that people don't really "talk" to each other anymore. I always say that I rarely see people actually chat on their cell phones anymore. However, with this instant form of communication, it opens up channels of activity unavailable to us ten years ago.
We used to write a letter. Then it would take several days for the person to receive it. Then of course several more days to wait for a response. Now, we we can send an email/text and within minutes or even seconds receive a response. This gives us the opportunity to instantly respond back and so forth. Communication is made easier and more accessible.
As for social networking sites, I have been able to get back in touch with old friends who I dearly miss. I can get a snap shot of their life by looking at their pictures and getting updates on their career path, where they live, etc. In turn, I feel connected to these people who I honestly care about.
There are obviously negatives to modern day communication and certainly one can feel disconnected. However, it also provides so many opportunities to maintain relationships that we otherwise would have lost.