Depends on the cause and the total prognosis.
This stuff is theoretical to a lot of you but pretty close to home for my family. My wife suffers from Multiple Sclerosis and there is always a chance that something like this could happen to her.
Her wishes have been pretty much to keep her alive unless there is absolutely no hope in the near future of some kind of pallation of the problem. Note I didn't say cure. With the modern research done today (ie stem cell) who knows what may come down the line in just a few years.
Personally, no, I wouldn't want to be kept alive but at the same time starving me to death is a particularly cruel way for someone to go too. I couldn't just starve my wife to death, especially if she has cognitive function. To let an oriented person starve to death has to be exceptionally cruel in my book and I couldn't do it.