DM: The raider's handaxe puts you into bloodied. Now the Eye of Grummsh acts. Speaking in Common he describes the torments you will suffer unless you surrender. What's your Will defence?
Player: 15. Why?
DM: With his +10 Intimidate the Eye makes... 26! You surrender. Next turn take off your armour.
Player: I surrender? What is this, mind control?! You're reading the rules the wrong way...
DM: Okay then Einstein, riddle me this: Why do Orcs get Intimidate?
-vk
To be fair, it was clever. The first time. When Lore wrote it. Anyway, why do orcs have intimidate? Same reason some 3e monsters have diplomacy.
I actually wrote up a pretty big (although rambling) paragraph talking about this and ended up deleting it because I thought it was off topic. But basically, many players bring to the game the implicit expectation that social skills (diplomacy especially, but also bluff and intimidate) do not work on PCs. This isn't true in every game, and is not required for a game to be fun. But it's not something you want to surprise people with.
For PCs I tell them you are convinced you can't win this fight, and if you continue to fight you will die. I let the PC decide what to do at that point. And I generally trust them to roleplay there character correctly. If someone has defined there character as being spineless I expect a surrender, but I wont insist on one.
Same thing for bluffs, cons, convincing arguments etc.