There are over 10.5 million Internet users in the Balkans/the former Yugoslavia, which makes up 51.7 percent of the region's population, according to a recent report  [sr; see the table below].
The findings  [.zip, sr] cited by Huge Media, in collaboration with Marko Tomić, a student from the Faculty of Organizational Sciences , University of Belgrade, show that Slovenia has the highest Internet service penetration (63.29 percent), while Bosnia and Herzegovina has the lowest (51.76 percent of Internet users).
It is interesting that over a half of the Serbian and Croatian population is on the Internet, and the authors of these findings consider  [sr] that there's an incomplete research evaluation of Internet usage by the Statistical Office of the Republic of Serbia  (RZS):
…As for the Internet users, we think that the RZS assessment is incomplete and does not include users of mobile internet. […they are] only examining a particular set of data that gives us information about a particular topic, but not the complete story that interests us.
Facebook is the most popular destination: over 70 percent of Internet users have a Facebook account in Serbia, and 63 percent – in Croatia:
The average time spent on Facebok is 25 minutes (both for Serbia and Croatia), and the average user in Serbia checks his/her Facebook account 16 times a day, while in Croatia it is 13 times a day.
The increasing number of Facebook users can be explained by non-residents of Serbia and Croatia using this social network during their travels.
The online social dynamics and the activities on Facebook do not differ much in other Balkan countries. Last year, we published the data on the Serbian young adults  who spend the most of their time on Facebook, communicating with their friends (61 percent), “like”-ing their statuses (66 percent), sharing content and information (56 percent), writing private messages (47 percent), and playing games (22.4 percent).
Statistical and educational institutions in each of the Balkan countries could generate and use the data on the relevant online activities to detect and focus on their critical users, to adjust their policies and action plans based on the data.
It would be also interesting to see age distribution among users and other relevant demographics, as well as the analysis of online social interactions on other Internet services and social media sites.
Currently, research  is being conducted on the social media usage among young adults, students, educators, and scholars in Serbia, but it is limited, in a way, as it cannot be considered a sample for the entire Balkan population. Each country could work on their local national data for cross-statistical area analyses for the future.