This is the US section of Answers, so we're not too familiar with French NGOs. But in America, two infamous NGOs are Fannie Mae and Freddie Mac, you've probably heard of them. 

On the pro-side, NGOs have the backing of the government, the most powerful financial force in a developed country. Because of that, they wield so much power that they can do things a normal company couldn't. Because they are government sponsored, special laws can be passed by the government that further enables them to do things other companies couldn't. 

On the downside, with great power comes great responsibility, and absolute power corrupts absolutely. In the case of Fannie and Freddie, they pretty much gambled with the US treasury and they lost that gamble. The effects are even more widespread and reach nearly every corner of the developed world.