Might I suggest without knowing what you mean by "plot" (given Xechao's definition of "any action taken" in a game) that you may be railroading your players? Which I fully understand some people like. Don't let my opinions stop you from enjoying whatever play you prefer in a game.
I don't think what I'm doing is railroading. If it is, then any DM I have ever met is railroading, and all players just love that. When I plan an adventure I have a good idea of what's going to happen, in general lines. That is because of a few things:
1. I know the goal, character and abilities of the PCs' adversaries and allies. Furthermore, I know what their plans are, what will happen if the PCs don't get in the way, and how these NPCs react if the PCs do.
2. I know what cool locales exist in my campaign world. I know how these locales may interact with the PCs and the NPCs.
3. I have a good understanding of both my players and their characters. I can usually expect their reactions to certain situations. Not always, granted, but still enough to go with.
Because I have a pretty good understanding of all these things, I have, as I stated, a pretty good idea what's going to happen and how that can unravel into a great story. The actions of the PCs would create a plot. It might be close to something I had in mind. It might be totally different. Still, it will have a sense. It will have a beginning, a middle and an end. I don't force anything on the PCs. At no point do I say: "Your characters do x,y,z" unless they are compelled to do that by some magic. Now, characters are always bound to do something unexpected and ruin all the plans I have been making. This is ok. Actually, this is great, and it challenges me to change my own plans so the game would still unfold into a great story, created by both me and my players.
Is that railroading? hardly.
Is there a plot? I guess it depends on how you define a plot. I believe there is.
Is it fun? you betcha. We are now on a few months hiatus from our Ptolus campaign. The players can't wait until we come back to it. Not because they really want to level up, and not because of the kewl equipment they may get. It's because of the plot. It's because they are attached to their characters, which are not just a placate, but well-rounded characters who have their own goals in the gameworld, which have a logical sense IN the game world. I know that without those things, they wouldn't have care less
what campaign we were playing.