Sorry, I saw it on my mobile, and meant to answer this.
Problems in the rest of Pakistan relate to terrorism, because Taliban/AlQaeda blame Pakistan for the US using Pakistan land to launch drone attacks etc.
Karachi is really far from that part of the country, and there is no problem with terrorism here.
Instead, there is a lot of gang activity and racial tension, which is the problem.
The Taliban are from Afghanistan, and the Pathans who have started migrating here since the trouble started are taking up jobs, and bringing there illiterate way of life to the bigger city.
It is sorta like the Mexican problem.
The Pathans situation:
* Are poor, mostly refugees of the tribal areas like NWFP and Afghanistan. Many are good, and try to get jobs working taxis, driving cars for people, busses, rickshaws, baking bread etc. Unfortunately, when you have an influx of the very poor into a well off city, you see crime go up. Some of these Pathans get involved in crimes like murder, rape, mugging, and home robberies.
* Because there is no screening for who is coming in, you really can't be sure if actual terrorists are coming in -- which I bet are.
* Other ethnicities like the Baloch have started to feel tension -- perhaps because they look like Pathans -- and a mini war between Pathans and the Baloch has broken out in the ghetto areas.
* The local governing political body, the MQM, has been very vocal, and have been apparently preaching hate behind the scenes. The MQM are basically the people who migrated from India and founded Karachi, and they've been voted as the local government. Apparently MQM hooligans have been hunting and killing Pathans. A lot of innocent people are getting killed.
Yea... that's about it. The main streets and areas are perfectly fine. But when I go to work, the staff who come from the ghetto type areas talk about how it is dangerous for them to even come for work.
So yea, definitely a lot more dangerous than the Mexican issue, but you get the idea.