I worry about stuff sometimes... no surprise to people who know me... A few possible civil liberties related issues get me thinking...
These have to do with very innocuous things that would not even be noticed most of the time. BUT, if you are stopped or detained for any other reason, these things can be added on to make you appear suspect. And since folks can be held longer in certain circumstances, which could also be more broadly applied in the future, these start to get a bit scary.
1: I think someday having cash in your pockets will be suspicious, since most transactions will be electronic. Having cash won't be be illegal, but suspect. Lots of questions about why... If it's in $20's, then were you planning to buy something illegal? And if you have change, you must have bought something with your $20's - is that vendor trying to avoid paying sales tax? etc. Even now, having too much cash on you can be viewed as drug related activity and property ceased without due process - of course it's quite a leap to just having $40 in your pocket.
2: As we gather more and more data, the likelihood of perfectly innocent coincidences will skyrocket. Mis-applied statistics will be used. "Sir, we noticed you drove past a mosque yesterday. And last week you were within 2 blocks of another mosque - what are you planning!?" The fact that you didn't even know they were there won't matter. The capacity to log data about your every activity and movement is increasing very rapidly, odd coincidences WILL happen, and statistics are still not well understood by many.
3: Sir, we picked you up in a neighborhood which is predominantly of (ethnic group xyz). What were you doing there? The catch is, here in California, there is no majority race anymore, and each county varies, so almost by definition anywhere you travel through won't be inhabited by your race or religious group. I certainly don't mind this, part of the draw of the Bay Area actually, but it's another bogus add-on for suspicion.
I hope these things do not come to pass, but sometimes the trends seem to point that way.
Even now, our traffic laws act as a writ of assistance for law enforcement. Virtually everybody drives over the speed "limit". And if you drive under it, they can cite you for unsafe driving, because you are not going with the flow of traffic. And if you got just under the speed limit, well, that's a profiling match for people running drugs! So no matter what speed you drive at, if they want to pull you over, they can turn that into a reason. In reality I don't think this is done very often, and if cops abused it I suspect it would make the local news, but it's still an odd situation.
Heck, even writing topical blog entries that contain certain keywords could flag you for a quick review... oops, gotta go! :-)