It would depend a bit on where you live and what your job is, but I am always barefoot, have been for more than eleven years, and it's working just fine for me!
You are correct, there are no laws requiring footwear, even at many places of work and certainly not for customers. However unfortunately a lot of places in the US set their own dress codes, either because they believe in the urban legend that it is against Health Department codes or because they simply dislike bare feet (they can require any kind of dress regardless of whether it's required by law, just like a restaurant can require suit and tie -they could require their customers to wear a red clown's nose if they wanted to). So if you're in the US you'll probably run into that kind of thing some of the time, and then it depends on how much you need that particular business if you can just go elsewhere or have to wear shoes to get what you want. In a small town you'll have less options, in a city you'll probably be able to purchase anything you need or eat out etc just by patronizing a business that does not discriminate based on appearance. In other countries --not just third world countries where health and safety rules are often ignored, but also Canada, Western Europe, Australia- signs and dress codes prohibiting bare feet are rare. I've never even seen a 'no shoes, no shirts, no service' sign here in the Netherlands, nor on my trips to Belgium and Scotland.
Driving barefoot is legal too; see source. Some cops are convinced it's unsafe and even though they know it's not illegal may try to write you up for unsafe or reckless driving, however please see the further links in the source, for two sites (one from the Michigan PD, one from an Australian newspaper) making it clear that driving barefoot is no more unsafe than many types of footwear that are regularly worn and could even be considered safer than many kinds of shoes.
As for the weather, many people believe we need footwear to protect our feet from the heat or the cold. Now while managers and other people can be argued with, it's no use arguing with nature, so if you live in a place where it gets very hot in summer or very cold in winter, it may be a good idea to carry backup footwear on hot or cold days just in case. However, as your feet get tough and your body gets used to going barefoot, you may find you need it rarely or eventually not at all. Our limits are much further apart than most people who regularly wear shoes think (or than you should attempt suddenly, without giving your feet time to adjust!). Think of how the aboriginals walk barefoot in the Australian desert, and I've seen pictures of Asian sherpa's walking barefoot in the deep snow on a mountain. Myself, I have little experience with heat (we hit 104F/40C for the first time ever in 2006, most summers only have a few days over 86F/30C), but by keeping the rest of my body warm I can go barefoot in temperatures well below freezing and I've even worked outdoors for several hours at a time in snow without any numbness or pain when warming up. I describe in more detail how I did this in an older question here: http://answers.yahoo.com/question/index;_ylt=AoIt3rAUSoDQqroo.cqcWijsy6IX?qid=20070109093943AA0LxLq&show=7#profile-info-710455a60e12f4954c90711d2688fbd7aa
(this was written at the start of the winter before last; my body is still getting more used to it. I haven't even needed my barefoot gaiters in the last two winters at all)
If you have any more questions feel free to ask, I do have email turned on but I don't check my Yahoo account that often so it may take a while to get back to you.