Let us share our experience here. It must have either been impossible for you to find who a particular phone number
actually belong to or you have been lucky with your search. Your answer is highly dependant on two key categories of phone numbers which you have been tracing. And I am sure you would have mixed results for your searches.

Registered and Listed Phone Numbers - Easy to Trace
One category of phone numbers you have been trying to trace is when the number is listed, either a land line from home or a business. This is the easy category which you can access by running a search on any of the big three search engines with the phone number or simply running your fingers through the business phone directory.

Cell Phone And Unlisted Numbers - Lookup With Reverse Phone Directory
This next category however, has stumped many people and the key reason is the source of the numbers, either cellular phone number or unlisted in nature. A lot of us would have thrown in the towels and believe that it is fruitless searching for a cell phone number or worse, an unlisted one. You might truly have to enlist the service of your friendly neighborhood private investigators. Well, think again.

Enter the reverse phone directory which helps to find is the owner of that phone number in question, be it land line or cellular, listed or unlisted. The reverse phone directory provides great depth and breath in their databases of personal details allowing you to search from personal details to background checks, phone or cell number ownership history, related service provider information and some even provide geo maps for reference. Hence the short answer to your problem is yes, you can trace phone numbers, be they listed, unlisted, cellular or land lines with a few clicks of the mouse.

So give private investigators a miss and do your own personal espionage with the reverse phone directory, albeit discreetly.