mmadsen said:
Sure, they should make the choice to fall -- just as they make the choice to engage in a romantic subplot or to build a stronghold -- but how do you make that a natural part of the game?
If you have a really motivated player who comes into the game wanting to win the princess's love then see her die, then go into a mad rage and spiral into a destructive depression, he can do that, but how do you make it more likely that your "normal" players will choose dramatic-but-suboptimal strategies?
I've seen two ways that can encourage this sort of behaviour (never actually managed to use it well myself however). Both involve disguising the sub-optimal nature of the choice:
(1) Make the path necessary. Perhaps the PCs
need to gain the co-operation of the princess. By getting the player hooked on the necessary affection, it is possible to manipulate the mood of the game for that player. Perhaps the princess bears a terrible curse, or the burden of the crown is heavy, or her family put intolerable pressure on her. In such circs, Good characters can feel compelled to help out, and can be required to do so secretly. When events overwhelm the relationship and the princess, the PC can be overcome with anguish and behave irrationally to preserve the status quo (I know because I'e played that PC!

)
(2) More generally, make the choice
appear optimal. Think of the seductiveness of the Dark Side. Maybe the PC can benefit from training, or contacts, wealth or secrets. Then slowly add in the downsides - the favours in return, the necessary white llies to disguise the truth, the absences that cause others problems, and so on. If you layer advantage and disadvantage aright, the PC can be persuaded that their future lies with the 'princess', and when she is denied to them simple greed, distorted through the prism of past secrets, can make the PC behave irrationally. (I've been here too - and ended up fighting the party because I believed a lover's lies and desires over the party's goals!)
It takes a good DM to pull this off. I think that the two important factors are:
(i) skill in portraying the central NPC(s), making them sympathetic and believable, even when they are outright lying to the PC!
(ii) knowing the subject player really well, so you know what buttons to push that will make them move in the direction desired (e.g. I am a sucker for melodrama, so my DM played on the love of the emotional rollercoaster and the moments of high drama to manipulate me into a Catch-22 situation).
Neither are simple matters, and it will take a talented DM, but it is possible with some players. I emphasise
some, as I do know that certain players will
never be drawn into these things because they never get deeply enough into their PC-play to lose sight of metagame consequences.
Still, if you want a supreme challenge in your DMing, this is certainly one of them, and it can be very rewarding to the player (other players might not enjoy it, however, as it will demand a lot of one-on-one gaming to set up the situation).