I have now conducted a few tests on my router and am led to believe if you are in an area someone elses router and dont have permission, you can hack the router, find out all their website history and view current connections. If you a WEP key installed on your router, this is the problem. Remove it and use another security method, WEP is hackable and can allow users through quite easily, i disallowed my laptop from router, then used certain software to generate the WEP, got on then used Internet Tracking tools. It's so simple, people can Hack your router! use WPA or authorised connections only. keep your router password around 8 letters with letters CAPITALS also.

See a big white van across the road? that could be the hacker

Simon.

No reason to get paranoid. In fact, a "hacker", if he really wanted secure information, would probably find other means than trying to get in reach of your wireless network.
Besides, hacker usually aren't interested in your-average-household-wifi-network. Those "vans" are usually cruising leechers, trying to steal some bandwith.

I do, however, agree with you, that wireless network are victim of nonchalance. Initially, a router gave people the household-computer-user the heebejeebees, because they were so hard to configure and setup.
Over time, the made routers good to go out of the box. A little more than plug and play, but barely secured. Most people don't even know how to protect their network, let alone know the difference of encryption on WEP or WPA/WPA2 keys.
What's worse is that these people leave their router login on default, so it only takes a quick google on the brandname, to look for the default logindetails. which are usually "admin-admin", or "blank-blank" anyway. It seems that protecting your wireless network has become a little more user-friendly, lately, but that's just from what I hear from people.

Please don't confuse the word "hacker" with "cracker".

Hacker definition:
"A person who enjoys exploring the details of programmable systems and how to stretch their capabilities, as opposed to most users, who prefer to learn only the minimum necessary" (http://www.catb.org/%7Eesr/jargon/html/H/hacker.html)

The definition doesn't say anything about using malicious software to break into other peoples privacy. The word your looking for in this case
is cracker. I'm tired of the media misleading the true meaning of hacker.