Why is the current Ebola outbreak different from previous outbreaks?
This is too long for a comment, so I put this in here: The main reasons are sociological. From the data I have read so far, this outbreak (actually these are two independent outbreaks, one in West-Africa and another one -not connected- in the Democratic Republic of Congo) is not exceptionally deadly in terms of Ebola. The death rate is about 60% which is extremely high compared to other diseases, but Ebola had reached up to 90%...

I think the main differences are that this outbreak struck in a much more populated area which has a very poor health care system (if you can call it like this at all). Then it happened in a border region, I recall reports about a traditional funeral of a Ebola victim which infected visitors, some of them crossed the border afterwards. 

Then it was completely underestimated in the beginning, because a lot of cases stayed unknown. This led to a wider spreading as people who got sick infected relatives and medical personnel subsequently. And although the reaction has been powered up a lot since then, it is still not adequate to contain the outbreak. 

Former outbreaks happened in rural areas which where easier to contain with a smaller number of personal, which is not possible this time. If you want to read further about this, I recommend the blog of Tara C. Smith which has been doing research about Ebola for some time and also worked in crisis response teams.
Especially interesting are these two:


A historical perspective on Ebola response and prevention
Addressing more Ebola myths