Now for the technical jargon. If a Nevada court is asked to enforce a non-compete clause, it will consider the time limitation, the geographical territory, and the hardship on the respective parties. See Jones v. Deeter, 913 P.2d 1272 (Nev. 1996). The first is the length of the time restriction. Nevada courts have upheld time restrictions of up to two years, but invalidated restrictions of five years.
The second factor that the courts consider is the geographical territory that the non-compete clause encompasses. This usually depends on how big the company is that is seeking to enforce the clause. If it's a local company, it probably can't keep somebody from opening up shop in another city. If it's regional or national, however, a court may decide to enforce a much larger geographic restriction.
Finally, the courts normally weigh the hardship on the person being restricted with the potential damage that the competition would cause to the business. This also depends on what the employee received in exchange for agreeing to the non-compete clause.
The next time you are asked to sign a contract with a non-compete clause, make sure that you are fully aware of the consequences down the road if your employment is terminated. You may be looking for another profession for a few years.