No one should be working without the approved maintenance manual applicible to that aircraft available. It is the final authority in how the aircraft is maintained.
Having said that, I really don't see anything wrong with using these forums. I believe that there should be more discussion. We are not exactly working in real time so I think we are fairly safe here. We can all learn from each other.
The internet is a resource and we should use all of our available resources to learn. Any 'advice' accepted should not be used without solid evidence it is correct just the same as if you were standing on the hangar floor or flightline asking someones opinion.
One of the biggest problems in aircraft maintenance is the fact that quite often there are few people willing to pass on knowledge. It's not easy to get a good handle on the basics when you are dealing with the newer technology but there are still enough old timers around to educate others. I believe that when a person wants to learn, he should reach out. This forum can be a very useful tool as long as it is used wisely.