ETFs are incredibly common these days, even for individual investors. They're very similar to a mutual fund. For anyone wondering what an ETF is exactly, or how one works, here is a good explanation:
http://www.investopedia.com/terms/e/etf.asp#axzz29kS9Cw8P
I'm going to back up Blondie and say that any large multinational corporation (including a non-profit) will invest a portion of their liquid assets in the market. Most of these institutional investors carry conservative investment mandates, so investing in something as historically stable as ETFs benchmarked against indices would be completely appropriate with that type of mandate.
To my knowledge, the WTS has never said "you can't" or "don't" invest, it has simply cautioned that doing so carries certain risks and not to invest in a way that demonstrates greed. Sorry, this just doesn't strike me as conspiritorial or hypocritical.
R_O