So I nicked this from (off of lol) YouTube
The educated classes have been using the word 'so' superfluously at the beginning of statements since the 90s, especially when answering direct questions. Linguists have traced it back to Microsoft employees. For me it is the most annoying linguistic habit to arise since the tendency (in the English speaking world) to finish non-interrogative sentences with the questioning inflexion.
This adoption of 'so' as a syllable to announce the beginning of a statement is often by the sort of people who would sneer at the use of 'like' to vocalise the comma or replace 'erm', which they see as a sign of a sub standard education, blissfully unaware as they are of their own ridiculous speech habits.
The effect of the erroneous use of 'so' is that I stop listening to the speaker immediately, as my own internal monologue takes over with thoughts like "This person is an idiot". 
And that's it in a nutshell