There are several things to keep in mind when shopping for an online background check service. As with any industry, there are a few less than reputable dealers out there. They may use all manners of tricks and loopholes in order to separate you from your money while providing nothing of real value.
Perhaps the biggest swindle is to charge exorbidant fees for public records. Records which are openly available to the public include criminal convictions, traffic violations, and civil judgements. All that is necessary to obtain these records is a request to the county government. Of course, you will have to search every county individually. Perhaps the only value these services provide is saving you the time and effort of searching every county's records yourself. However, the ease with which county records are obtained make this of questionable value. A similar scam is charging money for sex offender record searches. These records are free and in fact, actively distributed to the community by the local government. You should never pay for sex offender records. If you need to know if someone specific is on the list or if you need a list of all sex offenders in the area, contact your local sheriff's department and they will give you all the necessary information.
Also watch out for the words "international". There is currently no such thing as an international background check, due to the language barrier and incompatible systems of government. Any service which claims to be able to deliver records from any country in the world is likely exaggerating the capabilities of their service. Some background check firms have access to information from countries like Canada, Ireland, UK, Australia, New Zealand, etc. but that is pretty much where it ends (and these records are spotty at best).
Some background check websites are also highly suspect. Many of them do not even represent a real company but rather a fly-by-night online background check service (which may or may not be guilty of the swindles previously mentioned). To make sure you are dealing with professionals and not hucksters looking to make a quick buck, always look for a physical address and a telephone number on the website. Contact the company using the telephone number to verify that they are legit. You'd be surprised how often websites are simply affiliates trying to make money from gullible consumers. Even a service providing the most basic criminal background check will have a real address and telephone number.
Don't believe that background checks are useful for civilians? Consider the following story: a recently divorced man signed up on a popular dating site looking for a new relationship. He met a woman with a very attractive profile picture and the two seemed to hit it off in conversation. They continued talking for weeks and finally decided to meet in person. The only problem was that the woman claimed to live several states away, and wanted this man to front her the money for a plane ticket via Western Union. This seemed very suspicious, so the man ran a background check on the woman's alleged name. As it turns out, no such person existed in the geographical area in which this woman claimed to live. The man reported this to the moderators of the dating site. Upon investigation, they discovered that this account had been guilty of several such scams in the past, but were not reported (possibly due to the victims' reluctance to admit that they had been scammed). Law enforcement was alerted, and it turned out that behind the picture of the beautiful woman was a man out on parole. He had been in prison for wire fraud and had gotten back up to his same old tricks.