I don't mean commit as in she's looking for a husband or some guy who will creepily follow her around for the rest of her life. I think we need a different definition of commitment.
To me, commitment is delivering on the promises you make.
I don't mean this promise has to be explicitly stated. You aren't raising your right hand and saying, "I do hearby solemnly swear to uphold the Law of the Wolf Cub Pack and to do a good turn for others every day."
The promise is often in your behavior.
If you approach a girl, the unspoken promise is that you are going to be more interesting than whatever else is going on around her.
If you're expressing interest in her and then refusing to make a physical move, you are not delivering on your promise. Don't take my word for it. Check out this link.
If you say you want a casual relationship and then you spend every day with her, introduce her to your parents, and move in with her...you are delivering something different than what you promised. You are sending a mixed message and if things go south, you can't blame her for "not listening when you said you wanted something casual." Nor can you blame her if she decides you're being too clingy.
A big part of dating and relationships is trust. And part of being trustworthy is being reliable--doing the things you say you're going to do, whatever those things might happen to be.
Don't promise anything--in word or in behavior--that you aren't willing to deliver. Don't deliver something different from what you promise.
-May All Beings Be Sexy
Check out this link for information on how to get Dan's Dating for Shy Guys ebook.