Reasons to Apply for a Tourist Visa vs. Reasons to use Visa Waiver
The visa waiver program permits foreigners from some countries, including Japan, to apply for admission to the United States as a business or pleasure visitor for up to 90 days. The visa waiver program does not permit the foreigner to work, rather it replaces the need to obtain a B-1/2 visa. Foreigners who intend to work in the US must still obtain the proper working visa. Also, the visa waiver program does not permit you to extend your stay beyond 90 days or change your status to another purpose.
When you arrive at a US airport you must convince the INS that you are "admissible" or qualified to enter the US, and that you are telling the truth about your reason to visit. There are many legal reasons why the INS will deny a person's request to enter. Some of the main reasons the INS will deny admission are as follows:
There are "waivers" available to some (not all) of these problems depending on the facts of the case. These "waivers" must be obtained prior to traveling to the US.
Reasons to apply for a tourist visa rather than using visa waiver:
There are two general things that can happen at the airport if the INS denies your request to enter the US. The better of the two is that the INS allows you to withdraw your application for admission and you depart the US on the next plane. You then need obtain a visa before you travel back to the US. The worse of the two choices is that the INS will charge you with an US Immigration crime and officially kick you out. This will create a record and more trouble.
For more information visit my website at www.horitsu.com. There is an extensive discussion about B-1, B-2, and the visa waiver program in the nonimmigrant section.