Well that is a very good question. Although you can purchase and use an electric cigarette in your own home and vehicle, you still might have a little trouble using it in places like restaurants, bars, and other public places freely. Over the years there has been such a stigma attached to smoking tobacco, with good reason, that people have not yet realized that using an electric cigarette is completely different than smoking tobacco. When you use the e-cigarette it looks like you are smoking and this is what other people see. What they do not know is that there is no real smoke involved, only a vapor. They do not know that most researchers consider this vapor to be safe to exhale around others.
The vapor that is exhaled by electric cigarette users is only a mixture of nicotine, water, flavorings and a few other ingredients that are thought to not be harmful to people. Any ingredients found in the nicotine liquid are substances that are used in products that we already buy. The e-cigarette vapor dissipates and disappears almost instantly when it is is exhaled and there is no vapor at all expelled until the user inhales and then exhales. This is unlike a tobacco cigarette that smokes continuously when it is lit. It will most likely not be alright to use your electric cigarette just anywhere until the product has been approved by the FDA which could be very soon.
Once the product has been approved and the facts abut the safety of using the e-cigarette are widely known, it is expected that it will be legal to use your electric cigarette in most places. This is the hope anyway. Since it likely does not pose a threat to others, there is really no reason why it should not be. However, you can not expect the views on smoking anything to change overnight no matter how much safer it might be.
What is already great about using the electric cigarette in your own home or vehicle is that there is no offensive odor. There is no tar produced by the electric cigarette because it is never burned, only heated. There is no real tobacco in the e-cigarette, only the nicotine liquid. There is no sticky tar residue to stick to things like your skin, your clothes, your furniture, or the interior of your vehicle. These are just a few of the reasons to stop smoking tobacco and start suing an electric cigarette that is a much cleaner way to get your nicotine.