We respond instinctively to archetypes, and a lot of shysters take advantage of this. Yes, there's a lot of interesting, useful stuff about them (Hero With A Thousand Blah Blah Blah) but the reality is that if you come up with a list of, say, 3 or more things, and define it broadly, then it will resonate with people as a powerful model. Some of this is just numbers: If I list 8 types of Stamp Collectors and define them loosely enough, odds are good I've covered 90%+ of the potential audience, and that last 10% will probably find a way to make it work. A larger part of it is how our brains tend to glom onto data - archetypes (like stereotypes) are the chocolate frosted sugar bombs to our brain's appetite for understanding - they're tasty and they go down easy.
So, with all that cynicism established, I do want to talk about how they're useful - especially the ones you create yourself.
After my post last week, I was speaking to one of the subjects (the Rookie) and he voiced an interesting thought, wishing there was some way to note people's archetypes and then keep track of the characters they've played and see how those things overlap. We agreed that for a lot of players there's a comfort zone that they like to stay within, and there's a lot of value in pushing them out of it, but at the same time you don't want to push them too far out of it.
Now, doing this is tricky, but the first part of requires identifying the player's comfort zone, and this is where the idea of making your own archetypes becomes handy. See, an advantage of making archetypes for your players is that you can afford to not be entirely precise, but at the same time you're going to get more specific than you would with generic character types.
Once you've figured that out, you can do something Fred did, long ago, when setting up Born to Be Kings (The first FATE game, and my favorite campaign of all time). See, Fred knew his players and their tendencies pretty well, so as part of character creation he took each player aside and planted a single "flag" outside of their comfort zone. This flag was the one element he was imposing on the character backgrounds, and it served as an irritant to form a pearl around.
What's interesting was that each of us responded differently to the flag. One player who usually tends towards logistics had a fae element inserted, and jumped into it with both feet. Another player was uncomfortable with it, and that friction drove a lot of play. But one way or another it forced us all to play differently than we would have if we'd been given free reign.
Constraint breed creativity strikes again. Who knew?
Anyway, this is one of those ideas that not hard to implement, but may be tricky to implement well depending upon how well your players respond to structure and how much trust they have in you as a GM (especially if your flag would force them to make what they consider a non-optimal build choice) so you may need to learn how to strike a balancing act. This is easier in something like FATE or Cortex Plus where an Aspect or Distinction is rarely a "wrong choice", but it's still entirely possible with games like Pathfinder or 4e (4e actually offers some really interesting options for this with Themes), even if they are entirely in-fiction.
Anyway, when the time comes for you to start your next game, stop and think about your players, and how you can help them push beyond the archetype you see them in and into something more complicated, interesting and fun.