While word of mouth was considered important before as well, marketers couldn't really "get a hold of it", not to mention analyse it's effects and results. Now with the technology that's out there today it is easier to monitor the word of mouth activity that unfolds on the net. Of course this is just a part of the whole WOM phenomena, but we do have to consider two aspects in this case:
A. The time spent on the internet - an eResearch Corp study shows that 71% of the questioned population (the study had included 16+ year old's in the Romanian urban environment) uses the internet in an average of 3 hours daily.
B. The interaction happening on the world wide web - another study (sorry I don't really know who conducted it) shows that 95% of the respondents are unsatisfied with the real time spent with friends and family and 58% prefer meetings with F&F on the internet, due to time-effectiveness.
As you can see the results are in favour of WOM that goes on the net, and I believe that these figures will increase in due time.
Inbound marketing is much more data driven than outbound marketing and this is thanks to, again, the technology out there, so do not forget to analyse, analyse, analyse. Of course outbound marketing uses and tries to monitor the impression of a campaign, but with inbound marketing it's much more easier to gather the data you need to, let's say, categorise you marketing activity of a given period as successful or stillborn. But, it is not enough to collect the data, it is vital to understand it and to act according to it. When it comes to data you might like to check out Avinash Kaushik's blog, as it is one of the essential marketing analytics blogs out there.
As you might have guessed it's all about tech - inbound marketing being more technology based and technology driven than outbound marketing, although the latter is changing as well due to technology developments. This is mainly due to the fact that the majority of inbound marketing actions are linked to the world wide web and presume that the target market uses "technology platforms" (if we can call it that) that are more spread like the PC or laptop and/or the latest entries in this domain like smartphones, tablets etc. Additionally, it uses blogs, social media, QR codes while the reach and impact of paper-based newspapers and magazines, of the telly and other traditional channels is decreasing. It is important to note that I am not saying that inbound marketing will replace outbound marketing any time soon or ever in fact, a successful marketing campaign will include both in different rates, according to the end audience.