I've had this before. I'm a pretty open and honest person, so generally I end up feeling offended if I've developed an otherwise close friendship with someone (ie. I've told them some pretty deep stuff about me) and they never open up to me at all. I think I get upset because I feel like they don't trust me.
The conclusion I've come to is that some people have an innate desire to be an agony aunt to others and/or they find that focusing on other people's issues means that they can avoid having to think about their own. I've had one of these people allude to it being something like that. Some people are just very private I guess. I can't really relate to that!
Or, some people like to do that Knowledge Is Power thing, but in my experience they are relatively easy to spot over time. It becomes obvious that they're not really interested in being friends, they just want information because they have some agenda or other to push.
I don't know how to deal with this and be a bit more clever.
Not sure what you mean by being a bit more clever. Do you mean that sometimes you end up feeling self-conscious cos you've shared too much? Or people use that information against you? I used to feel like that a lot, but I've decided that I am who I am. I
try not to overshare with people I don't know very well (or whom i suspect don't have my best interests at heart), but I hate feeling suspicious of other people's motives. It wears me out second-guessing people all the time, so I'm working on trying not to worry about it so much. I like being open and honest. I don't want to have that stolen from me. If that makes any sense.
I'm sure there are hundreds of other reasons that people do this, that's just my two cents from my own experience :).