Great observations Jim. I would say a large increase in frontcountry fisherman and a marked decrease in backcountry anglers. If you read posts on forums like this you may get the idea the backcountry is crowded with anglers and there are waiting lines to fish three forks etc. but most of the time its the same 6 or 8 guys posting these reports. The fact is the backcountry it is pretty much void of fishermen in 95% of the park. Even on nice weekends in summer most campsites are empty and hundreds of miles of stream sit untouched. Backcountry camping is currently back down to the same level as 1960s which is pretty incredible. Nowadays it seems everyone sticks close to their cars. On a hot summer day you will find great packs of folks swimming and enjoying the waters on lower Deep Creek, the Townsend Wye and up Tremont Road, but they tend to congregate together (for safety I theorize) so if you go to a smaller stream or branch it is very easy to find complete solitude. Item #10 on Jim's list may be one of many reasons for smaller bows ie overpopulation.
Here is another couple of obvious ones:
The opening of brook trout streams to fishing although open for a while now many of the signs prohibiting speck fishing still linger around the backcountry.
The ease of learning about fishing the park on internet forums such as these. Ability to learn anything and everything including stream names from time to time