It is not the intent of this help forum to resolve or advise on legal issues for which any local user may be held accountable in matters of either civil or criminal law in their jurisdiction. Nor do we condone by advice or example any conduct that is restricted or prohibited by law.
Rather, it is our purpose to assist members and readers to better manage and secure their own computers and networks such that their own practices insure best possible safe, legal, and successful use of their own equipment.
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As to the topic of accidentally, opportunistically or intentionally gaining access to WiFi internet connection, the activity is casually known as "leeching". The term refers to a creature commonly found in nature, usually in a body of water, which attaches itself to the body of a host animal for the purpose drawing nutrient substance from the blood of the host. While, in medical application, there may be beneficial applications known for the use of "leeching", most common thought and experience deems the idea of becoming personally infested with such creatures to be disgusting, dangerous and to be avoided. In that regard, the internet community has aptly termed the use of internet access that doesn't belong to the user as exploitative in a disgusting and dangerous fashion…
leeching.
Think of it this way…
If the front door of a house is open ,you have no right to wander in. And if you take something it's a crime.
An open access point is like an open front door. If you use the access point to get onto the Internet, someone has to pay for the bandwidth - either the owner of the access point or their ISP. Something is being "taken". And if "taken without permission" could be considered a crime.
If you have a WiFi card and connect via another person's access point/internet connection, it would be pretty easy to convince a law enforcement authority that you've done something wrong.
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For the reader's information, there are laws in the United States and most other jurisdictions world-wide that apply to this topic.
The initial law here in the United States appears to have been drawn up as a matter of national security in 1985. Reference to this legal body of information can be seen at:
http://www4.law.cornell.edu/uscode/html/us…30—-000-.html
WTT makes no claim as to the reliability, accuracy or application of this information as it relates to the readers own legal jurisdiction.
Most States have crafted their own civil and criminal legislation on the topic, to which the reader should refer in their own specific case.
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Interestingly, various businesses have widely differing attitudes and practices regarding the practice of "leeching".
For instance, in the travel/tourist trade some hotel/motel chain have found that making unrestricted wifi access available, actually draws potential customers to stay at their lodging, and may in some cases promote the free use of wifi connection as a way of attracting business from passers-by on heavily traveled highways.
In some other instances, residential apartment owners have resorted to offering free wifi access as a feature of their contract much like availability of cable-tv or exercise and pool facilities. Apparently, the practice of "leeching" from nearby apartment neighbors became so common and annoying to residents that some apartment owners gave in and decided to make wifi available to all of their residents openly, instead of condoning one neighbor leeching from another.
And finally, there is the matter of the source ISP. Some ISP's have apparently supported free access sharing, while others take a highly restrictive attitude towards use of their bandwidth.
There are instances of individuals who have been prosecuted for "leeching", and the news has picked up on cases in States of Maryland, Michigan and Florida. Other states, no doubt, have cases on the books.
It may come down to this:
Leeching happens.
You as the owner of an internet connection have an interest in how that connection, which you are paying for, is used.
Password protect your Router.
Encrypt your wireless broadcast.
Stay safe, rather than become sorry.
Best Regards
My network was set up by a genius like you describe you do for your clients, but in any event, I wouldn't mind if you lived around the corner from me for checking purposes.
Congratulations too, I see a little purple in your status these days….well done and very much well deserved.
kind regards, 
I went on a trip to New York to the West Point military base with a group of network security students for a college program we were involved in. On the way back I was using my laptop and we got stuck in a traffic jam on the express way. So, I fired up my network stumbler and began pulling up networks located in houses off the express way. I was able to login to the routers with default passwords and change the admin password (I wanted them to be secure) before the cars moved too far to get a signal. Needless to say, as ridiculous as it was, we were all tickled pink being we were on a trip strictly for network security.
These are great stories of why people should encrypt their networks. Most people are happy if they can just get the router plugged in and working. If the network is called "Linksys" they could care less. 