What are the advantages and disadvantages of orangutans?

advantages--they are a critical part of the environment they evolved in (as are all parts of an ecosystem), their protection is helping save parts of the habitat that they evolved in, as a species the study of their behavior, genes and biochemistry give us a greater understanding of the natural world and evolution, as a great ape the study of their behavior, biochemistry and genes gives us a greater understanding of man and his evolution,

disadvantages--they take up space in the environment/habitat that man wants to use for his own gain, their conservation costs money because man wants the habitat for logging and farming and it has to be protected

No offense to the student, but that question shows a near complete lack of ability on the part of the teacher.  It is horribly anthropocentric, it assumes knowledge we don't have and it gives a really warped view of biotic interactions.  The question is idiotic. Advantage or disadvantage for whom or what?  The environment, the Orangutan, the other species with which orangutans interact?  The answer must be entirely different according to the assumed viewpoint.

Orangutans are a successful species.  That's all that matters.  Impacts they have, such as ripping up vegetation to make nests, are probably providing some opportunity to other species.  We don't know.  Rainforests are incredibly complex in their interactions.

Biology is science.  Science is a way of knowing based on observable fact.  This question, though close to meaningless, calls for assumption.