How the investment fund industry works is that the fund is charged a management fee by the fund manager, and that entire fee is now subject to HST. From that fee, various items in running the fund are charged. Because that fee right now is entirely subject to HST, all the expenses of running the fund are now subject to HST. That makes it a much more expensive investment product than other financial instruments on which you would not be charged HST.
On October 21st, 2010. See this statement in context.