I'm sure there has been an article on it (what hasn't there been an article on?...lol).
I've personally never read or heard any blanket injunction against investing, just cautions against very risky speculative types of investments. Anyway, the WTS itself has hundreds of millions in investments. The notes on their Financials usually say something along the lines of how they invest in instruments that "do not conflict with their Christian Conscience". Generally the investments are in fixed income safe stuff, from what I've seen. The Society usually sets a target of a few points above the annual inflation rate for their investment income. Because of the low rate of inflation lately, and the huge amounts invested, they usually meet that target.
Expatbrit