I couldn't possibly read everything here. I post on 2 other internet BBs and read a third (but rarely post), and I don't read everything on those sites either. I tend to stick to the areas that interest me.
On this board, I regularly read General Nursing Discussion, Polls, Nursing Activism, War & Terrorism, and Off-Topic. I'll venture into other sections occasionally if I have a question or see an intriguing thread in the "new posts" search.
Even in an area that I frequent, I may go into a thread and see that it's going in a direction that doesn't interest me, or see that that it's turning into a giant flame-fest, and I'll make a mental note to bow out. Or I may see that I hold a minority opinion and entering the debate would entail my having to do some research and pull up some articles or cites in order to illustrate my point; and I just don't have the emotional energy--so I stay away.
Depends on my mood and what's going on in the world outside, too--some days I need some silliness; some days I want to talk about world events; some days I want to debate; some days, as the Brits say, I just can't be arsed about any of it.