What are sovereign wealth funds? Why are they controversial?

What will be an ideal response?

Sovereign wealth funds are a new and controversial source of capital. They are government controlled pools of capital that invest in a variety of industries, mostly in a passive way. Most of the SWFs are owned by oil-rich governments. The Abu Dhabi Investment Authority is currently the largest, with $627 billion in assets, followed by the Government Pension Fund of Norway with $557 billion. Other SWFs are owned by governments of countries enjoying large balance of payments surpluses, such as China and Singapore. The funds are controversial because they should be solely for commercial purposes but could be a backdoor means of promoting the political goals of the governmental owner of the SWF.