Most everybody has gone to facebook for several reasons. For me it is the following reasons I am using facebook:
1. Real-time conversations and instant response times from the people you need information from
2. The ability to edit or add information as it comes to you in real time
3. Easier faster picture uploading and the ability to save pictures in large groups or albums, permanently for easier viewing
4. The ability to instantly share large PDF files and excel spreadsheets, etc (brochures, machinery lists, high resolution photographs, etc)
I still check in here 1 or 2 times a month but usually the new information I see here is information or pictures that I have already seen on facebook. The people I connected with on these forums are all on facebook and most are uploading all their pics and information there. I rarely log in here anymore but your question is a legitimate one and I felt I could offer and answer with one person's perspective (mine).
The threads here are cool, but now we have whole facebook pages dedicated to certain manufacturers or certain logging operations. A thread here becomes a whole page over there. The other issue is nearly everyone has a facebook page now and pics or info posted there reaches a much larger audience than we have here.
All that said- am I ready to give up on these forums? No. They have value and there is a wealth of great information here posted over the last 10 years or so.
The 2 are very different. There is value in both.
I hope that helps?