Having established a wireless connection (as per how to set up a WLAN) it is best to now secure that connection.
It's probably exaggerating it a little to give the impression that every Tom, Dick or Harry is out there breaking into wireless networks and that such an tivial exercise is trivial. Someone has to have the time, expertise and inclination to bother to do this.
You have to ask yourself: in general is someone going to bother themselves sitting outside my front-door to collect my wireless traffic? In the majority of home-user cases this is not very likely, and by taking the, albeit basic, security precautions available this threat can be reduced to what are probably acceptable levels for most folk. If you are really paranoid, then yes stick to a wired LAN. If you are a commercial operation things are, of course, different as this link from the UK computer press a while ago ago shows.
But even for the home user it is still worth the effort. The major options available are:
Not all equipment is currently WPA-enabled, but in the meantime by using the currently available techniques security for a home LAN can be maintained except in the most determined of break-in cases.
Thus the following miniumum should be carried out:
Other guidelines can be found at the Netgear wireless site link, for example: