In addition to the potential effectiveness you mentioned above, I think another key advantage here is bang for the buck. Online advertising can cost a fraction of what traditional mediums such as newspapers, television, radio etc. cost.
Overall the effectiveness of the advertising medium relies upon delivering a relevant advertisement that leaves a lasting impression, using the right type of delivery mechanism (e.g. Video, Display Ad, SEM, etc.) targeted to the right audience using advanced targeting algorithms. If Snakk can master this in the face of fierce competition they will be a success, however it would pay to bear in mind that even companies such as Facebook who have a treasure trove of data to mine for targeting purposes, still have issues with advertising relevance. It is an exceptionally difficult skill to master.