The internet does not suffice as a meaningful basis for discerning human behaviour, precisely because 'being on the internet' is indicative of only one kind of human behaviour (being on the internet). Okay, one may be able to access and assess the opinions/likes/dislikes of those who are willing to give them, but to what extent?
The OP assumes several things about the internet:
1) It is frequented by a huge population of humans.
2) All/most of them either do, or are willing, to give a honest and extensive evaluation of their everyday behaviour.
3) That something definitive about humanity as a whole can be hypothesised via analysis of such data.
However:
http://www.internetworldstats.com/stats.htm... This recent data suggests that, even now, less than a third of the world's population has access to the internet. What it doesn't tell us, is how many of them have regular access to it, nor how their opinions are constrained by the particular restrictions/impositions/fears/etc. which are specific to their locale.
Indeed, one should consider that even we in the 'free West' understand that it is not okay to give an honest opinion about everything, given the taboos and political correctness which are currently moulding Western thought. It would not be wise, for example, to proclaim to the internet-community that one was a facist/nazi/racist/paedophile/etc.. The point being that even 'the lands of the free' impose their own paricular kinds of restrictions upon what we are allowed to be honest about.
The bottom-line is that any data we have of human behaviour, discerned via a meta-analysis of global [internet] input, is not going to unveil anything significant about humans themselves other than the fact that [in general] their input does not transcend social/geographical/political/historical/legal/religious concerns. However, we already know that [now]. The internet just serves to emphasise this knowledge.
Sociology will never be [purely] like maths/science, even if it partakes of it, because there is no maths or science to Marxism/religion/Nazism/justice/equality/love/hate/fear/etc..
Sociology is a mongrel, in that it feeds from numerous/diverse practices (I've just studied it as a 3rd-level module for my degree, so am fully-aware of its extensiveness and limitations).
Il messaggero non e importante.
Ora non e importante.
Il resultato futuro e importante.
Quindi, persisto.