I have to say my main reasons not to let others on my internet connection are:
i dont need people using my broadband that i have to pay a premium for.
i dont want people on the net with my ip so anything they do gets tracked back to me
i dont want to have people near my network even if it is "locked from the wifi" ( security is a big problem and even though you may think you are safe, there are usually ways to get around things)
and of course the whole bandwidth thing, if people want to use my internet (take nieghbors for example) they can pay a small amount to cover my expenses and time to setup and maintain the service.
i think free wifi hotspots are great but remember, most free hotspots use advertsing to cover expenses, i dont think some big company like maybe bestbuy is going to pay me to advertise on my open hotspot at my house :D
i have 3 wifi aps in my house (dont ask why, :)) and 2 are open and one is secured. but the two open ones dont get good enough range ( so if someone was on my network they would have to be in my yard by my window) and the one that has the better range is secured so people cant get onto it.
i really think its your own choice. if you want to provide free access and try and keep yourself secure from people using it go ahead, your the one paying for the internet so you should be able to decide. But if you choose not to share your internet the same applies, your paying for your connection so you can choose not to share it with others.
i would recommend using some type of firewall/router box in between your wireless access point and network/computer if you do decide to open up your wireless
you probably would be surprised at how many wardrivers there are out there, and with long range antennas selling for 50$ or less ( see here:
http://www.cyberguys.com/templates/s...sp?T1=202+5697 ) just about anyone can get the tools to go out and "do a little damage"