I have learned, over the past six years of playing this game, that Sims seem to have their own mind in that they know whom they love and what careers are best suited for them (past the initial join the military wish). Wants do play a part in Sim lives but, some wants are totally triggered by the game such as make pancakes for breakfast will 'mostly' trigger a want to make pancakes (which I grant by-the-way, hey, they have to have something to eat tomorrow morning ;)). The 'Meet Someone New' pops up all the time for Sims with the Charisma trait or, when they want new Sims to talk to. I have only seen this icon used to indicate a desire to break-up when there are other tell-tales signs of unhappiness such as, refusing to share a meal together or a desire to go to the Park, Art Museum or any place other than where their partner is.
@ShuffleJ - I am equally fascinated by the double lives some Sims seem to lead, from Rabbit Hole Romances to hidden agendas within (townie) households.
@igazor - I don't believe in randomness in this game and view most things as either 'triggered' or 'communication to player'. I do believe the appearance of some wishes are rooted in what the Sim is wanting in that specific moment of time. Such as when I have my Sim learning to play the Bass and he suddenly sends up a wish to go fishing (complete with the fishing hook icon in his thought bubble). Barring fickle teens who seem to cycle through emotions more rapidly than the other life-stages, Sims seem to be very consistent in their desires, even when those desires change. Although, I can only speak from my own experience with my Sims.
@Mikezumi - The only time I have ever seen the game use the wish system as a hinting system' is with World Adventures, where a Sim will want to find the hidden door or disable the trap which is hidden right in front of them. This isn't to take anything away from what you stated as your perspective of the game, just happened to think of a time when 'hinting through the wish system' is used. :)