We don't need their energy because Somalia has some of the largest oil fields on the planet. If we get Qatar or Turkey to help us extract it we will not need Ethiopia.
If we depend on Ethiopia for energy that is going to really hurt us in the long term. Being dependant on another country for such a vital resource is a stupid idea.
Not proven, this is speculation based on the region's geology.
To date nothing has been discovered, and there is barely any ongoing exploration because a) Oil prices remain relatively low 2) The political risk doesnt justify the investments, even in relatively stable parts of Somalia/SL/PL where there is zero agreement on territorial boundaries.
Look at Kenya which only just started extracting oil last month, after a much longer history of exploration. Its already facing problems too:
Britain's Tullow says Kenyan protesters block oil trucks Im sure potentially interested parties see that, and project much greater risk in Somalia.