I don't have a problem with a DM asking for help online because a DM is the biggest cheater anyway, he's supposed to be a cheater so he can run a great game. Of course it's impossible for the DM to have all the answers, so I see nothing wrong with a DM posting online for help. The help he will recieve will improve his game for the players.
But a player isn't supposed to have all the answers because his PC won't have all the answers. People use the argument, "My Wizard has a 20 INT but I flunked out of Highschool....I can't roleplay him appropriately, so I need the help". I don't think that's the correct way to look at it. You also don't have a 20 CHA (well only a couple of us don't), but I'm sure you don't post online for help on how to roleplay your Bard romancing a barmaid and impregnating her that night. That's what skill checks are for. Just because a guy is a Rocket Scientist doesn't mean he has a better chance at problem solving a riddle or surviving a confrontation than a guy who fixes car engines. People like to think that just because you have a degree & work for NASA that you are overall smarter than people who don't. This isn't true...you are book smart in your area of expertise, but that doesn't mean you can't be stumped by a riddle or a puzzle like everyone else or be out witted by a college dropout.
I work at Stanford University and am surrounded by smart people all day long and I never went to college. And I can tell you one thing, most of the people I meet who are really well spoken and smart guys have the common sense of a stink bug. They are great mathemetitians or english majors, but if it doesn't have to do with their major, it's like dealing with a child and teaching them about life. They need their hand held just to deal with everyday life outside of their career. It's impossible to play out a PC's ability scores because there is no correct way to immitate it, life is too random.
For me, I prefer my players gain their knowledge strictly from the resources I provide in or out of our game. I wouldn't mind them reading online and learning interesting ways to use their skills/spells. It's just when it's a specific obstacle that they go online asking for advice on how to overcome it that I have a problem with. For example, if the player just learned the darkness spell and wanted to learn how to use it effectively in game, it would be ok to me if he got advice online about good combos with the spell. It will help make our game fun for me because he'll be challenging me in return, but on fair grounds. But, if he knows he's about to fight a Mind Flayer & tackle a puzzle in the next room, and he goes online asking for advice on strategies vs a Mind Flayer & opinions on the puzzle, that's not cool. As a DM, we setup the encounter to challenge our friends, not the entire online community. If you're a smart wizard or skilled fighter, roll knowledge or sense motive checks to learn what you want to know if you have problems. If you have problems dealing with an NPC, play it yourself & use skills if it will help. If you fail, then your PC just learned from it & can use that knowledge next time. Yes it's a game, that's why you're playing it. There is a reason that the PHB doesn't come with a chapter for strategies vs specific encounters....you're supposed to have a hard time against them and overcome it on your own, that's what a game is. Finding out ways to overcome challenges outside of the game is no different to me than reading the MM and finding out ways to defeat it's defenses. That's exactly what getting advice is, you're learning how to bypass defenses more easily.
Of course this is just my opinion for my own game. Everyone plays differently & I understand that. I just view that type of action as being the same as someone reading strategy books on how to walk through Baldur's Gate....not my cup of tea. But if the group & DM is ok with it, then I think it's perfectly ok.