Are social phobia cases on rise, being the Internet and mobile phones with cameras the main cause for their rise? That's an hypothesis I have, that I believe makes plenty of sense, anyway I haven't found any article about that, although it's not like my search has been exhaustive.

I mean, years ago, on the case you were caught doing something that society finds unusual, the worst thing that was likely going to happen to you were that some people around you, maybe a whole village if you lived in one a bit little, heard rumors about what you did and you had problems with that people around you. On some rare ocassions what you had done would get to the news and you will be highly exposed on the whole country, but it would be extremely strange than more than that would happen.

But now if you make something unusual, there are plenty of people that could record what you are doing and you cannot possibly be aware of everyone, and if you are caught and the video of you is uploaded, for example, to a good bunch of social networks, you are in danger of hundreds of millions of people watching what you have done.

So this looks as a good reason for an increase of social phobia cases.

Are there some studies that confirm my hypothesis?

Thanks.
Studies have been done to see how technology can alleviate social phobia, by communication through the net. (Yen et al 2012)

Heavy use increases (general) anxiety: (Anxiety was measured using the Beck Anxiety Inventory.) "Logistic regression analyses indicated that heavy Internet use is associated with high anxiety; high cell-phone use is associated to being female, and having high anxiety and insomnia." (Jenaro et al, 2006) *2 A replication of this study with a comparable population might answer your question.

Other studies have shown that "social phobia was associated with the risk for smartphone addiction in young people." (Darcin et al, 2016)

A study published 2009 sets the prevalence rates of social phobia at "in community samples of children and adolescents also vary considerably, ranging from 0.9 to 13.1% [26]. The highest rates have been noted in studies of older adolescents and young adults ", and sets the numbers for the whole population, quoting other articles,  "3.9–13.7% in Western societies" (Gren-Landell et al). 

The prevalence numbers seem to vary wildly depending on how the research has been done, as Furmark (2002) points out in his review of epidemiological studies from the 1980s onwards. - Doing this with current research would give more of an insight into your question.

So I'm sorry to say I couldn't, so far, find a study that specifically addresses your issue. :-(