Global Corruption Barometer
Just for fun, click on the above link (a PDF file) and check out Table 6 at the end of the report - page 22 to be exact. This table lists corruption's impact on different sectors and institutions by country. A value of 5 is extremely corrupt and 1 is not corrupt. What's interesting is there's an NGO column. And in countries like Turkey, Pakistan and Serbia there's a strong belief that NGOs are pretty corrupt. (I have a feeling you'll be a little surprised at the perceptions in other countries too.)
This illustrates the point of how important external perception can be in establishing context. If there's a cultural belief that NGOs are generally corrupt where you're working, you definitely should be factoring that in to your security plans. Always remember that perception equals reality.