Great question and one which I personally have stuggled with in the past few years.....believe it or not....considering I own this site, and ultimately are contributing to the very question that you are asking.
If you are focusing your question "only" on whether or not someone can "find" your secret spot by looking on the Internet, then my answer would be different than if you are referring to other factors which can negatively impact our fishery, such as its health, pressures, or environmental conditions, of the fishery due to someone reading something on the Internet.
Providing information that will allow people to figure out where you're fishing and what you're catching "used" to be something that was accepted and welcomed by all when fishing sites first started. The success of attracting people to Fish-Hawk all started off with the Ontario Map Project, and many fishermen who are still on this board, and have grown in their angling success, have used these maps to find spots, catch great fish, and improve themselves to the point where they are now finding "their own" spots, simply because they've expanded. I do understand now that there is often a lot of time, money, and trial and error that gets put into finding these wonderful little honey holes, where the fish are plentiful and big, and that sharing this information with others "could" cause a flow of anglers to those spots who in turn may fish it to death, and then that spot which was once a thriving fishery, now sees pressure that it didn't before and subsequently becomes just another spot.
It is for this reason that I've changed the way the Ontario Map Project works in that I don't mark the places where people have caught fish, but simply provide the maps, a little information on the body of water, and a discussion area for people to talk about catch locations "if they want to". It is purely voluntary. There are some who like to share spots, and then there are others who don't. This is perfectly fine since our Ontario Resources are for everyone. It is also the reason that I don't "encourage" people to tell others where they have caught fish and identify bodies of water any more....and then taking it one step further promote the idea of taking pictures and sharing them, but putting a little more thought into the positioning of the person who you are taking that photo of so as to not identify anything particular that would give away the spot that you may have found. It's not that hard if you just turn the boat a little away from the shoreline and take a close up shot of the person and the fish. This way you get to share your catch with everyone without giving away where you caught it.
Now for those who don't mind naming spots and sharing information with others, then that's their right as well, however the people who are on the recieving end of this information should take into consideration that even though you may have been made privy to a great location for fishing, you still have the responsibility to do what needs to be done to preserve that resource and even to respect the person who gave you that information by keeping it to yourself and not getting into specifics with anyone else, unless you have their permission to do so. In this case I'm talking about "private conversations" between two anglers.
Apart from just naming spots, there are a lot of other factors that the Internet now offers which were not available some time ago. Many of these factors contribute positively to our fishery, can increase awareness of it's sensitivity, identify how to properly do things, help us understand why certain regulations are in effect, help us learn new technologies and new products on the market, and help people build relationships...both personally and professionally.
This is my primary and number 1 reason why I do this, which is why I take it so seriously in trying to make a site which respects one another and shares information to educate and perhaps even provide experiences to some who actually never get to do what many of us do, and can only read and dream of doing it. Done right, it's almost as if the reader was there themselves, and to many that's priceless.
So......since I still maintain this site, my vote is "no", provided of course that at the same time it "brings awareness" to anglers so that everybody understands proper ettiquette with other fellow anglers, and most importantly, is aware of effects in the world which affect our fishery. These being such things as Environmental effects, Economical effects, Biological effects, Social effects, Water Body Pressure effects....etc.
It's all a part of the equation, and just like everything else in the world is not really as simple as focusing on a single question of whether or not the Internet is good for our fishery or not. It can be, and for the most part is, if used properly
Just my off the top 2 cents.
But there is so much more to fishing than being were the fish are. Sure you can read about some great location on some great lake. But you still have to learn on your own, and on that given day what it takes to put fish in the boat. The world is always changing. As are the fish, tech, and equip. it is a never ending circle. 
