While I agree that any decline in interest may be due to the failing economy there are two other factors worth considering. There is constant pressure on the part of manufacturers to continually "upgrade" their products at higher prices making the hobby a more exclusive activity. In addition there is such a proliferation of synthetic fly tying materials. Many producers will be promoting the same or slightly different items claiming that theirs is unique. Most of this "bull" really turns-off mature tiers but we see many newbies being encouraged to spend fortunes on stuff they don't need. We even see some of the most famous and published tiers continually producung new designs calling for exotic and strange materials.
I may sound like a minimalist but this is far from the case. I too am a victim of all of the above.