This is in some ways a difficult question because the issues that have caused the uprising in Yemen are not explicitly related to geography. Instead, the uprising has mostly been about the poor economic conditions in the country and the corrupt and autocratic nature of the government. The question, then, is how to connect these issues with the geographic location of Yemen.
One can argue that Yemenis are upset with the economic conditions in their country partly because of their proximity to Saudi Arabia. Saudi Arabia, of course, is oil rich while Yemen is the poorest country in the Middle East. This juxtaposition might help to drive discontent among Yemenis.
One can also argue that Yemen's geographic location makes it more likely to have developed an autocratic government. Essentially all of the governments in the region are relatively autocratic. Because of this, it is not surprising that Yemen would have a similar government that would breed resentment among the people.
In these ways, you can argue that geography helps cause the conditions that have created the uprising. Of course, what geography really does is to make the uprising significant to the outside world. Any instability so near to the oil fields and the Persian Gulf and the Suez Canal is relevant to the world as a whole.