There is no clear guidance of the personal domain names being registered on the internet. However there are quite a few court rulings where you can just assess the ability to use other person name for your profit. In short – do not do this.
However if you are planning on making a fan site without any profit (though in this time and age in all sincereness I would advice against the practice) you are welcome to do so but if the celebrity having that name asks you to cease and desist or hand over the name you have no choice but to comply.
The domain personal names are usually a clear cut case for UDRP as well, all one needs to do is to prove that it has such and such name and this is almost a ruling to get the name. Of course the gray area comes when two persons have the same name then the bad faith on the side of the person holding domain name must be presented.
We at Vastus Domains seldom have personal domain names for sale or backorder and even if we do, they are requested (backordered) by the very same persons having the name in real life. However there are many domain name squatters which are holding celebrity domain name for pure profit. If they get caught doing so they are in for legal proceedings and hefty fine and damages. If not they walk away with money. This is not gray area however, this is in my mind pure theft.
The problem with the legal side of things regarding domain personal names is that internet is international and while court ruling can be made in United States this does not oblige for example Sweden citizen to comply. ICANN can and does enforce UDRP for such cases meaning the court ruling is being enforced and name returned to rightful owner but for damages and fine they can not do anything.
To summarize, do not buy personal domain names if you are not the person holding the name in the real life.