Smart cell phones in a lot of ways are like mini-computers, because they browse the web, store and send email, store pictures and other pertinent information, and also keep a historical record of all of your activity. While data can be stored in a cloud, much data is commonly stored on a micro SD card specifically made for cell phones, and/or SIM cards, and also data is stored in flash (ROM) memory. As a user of a cell phone, you often don't consciously care where your data is stored, how your data is treated, or anything to that effect, but in actuality you should care deeply about this.
For instance, a brand-new cell phone will, by definition, have none of your personal information on it. The cell phone will have however the programs, directories, and the operating system necessary for your smart phone to function properly but the balance of the storage information on that phone will be unused, only awaiting your input. Once you begin using your smart phone, data will be stored, further, data that you delete will often not be deleted from the phone itself but merely be put into a different directory or location of the phone, to which it may or may not ever be permanently deleted, depending upon a multitude of factors.
People upgrade and replace their phones quite often; some do it as often as once a year or even more frequently depending perhaps upon whether they have a contract with a carrier which promotes more frequent upgrades as part of their plan. Some consumers upgrade every two years, and others upgrade only when they feel out-of-date or their phone is malfunctioning, or when they have the extra funds. When upgrading, for some people, they have no choice but to turn in their phone, to which they are promised that their previous cell phone will be wiped clean by the vendor, whereas some people sell their old phones, and others simply allow their phone to gather dust.
In the cases, to which you voluntarily relinquish your phone to your vendor or sell your phone, it is inherently your responsibility to protect your personal information, to which your smart phone may have an incredibly amount of both compromising and sensitive information that you would not normally desire to be in the hands of someone else, yet this mistake happens all the time. While I do commend the people that perform a system reset to their phone, under the belief that this will permanently erase all personal information, the sad fact often is that your personal data is still on the phone mainly because the data has only be re-allocated on the cell phone, but not truly overwritten or truly erased.
For all practical purposes, a system reset is simply not good enough to erase all your personal information. Instead, you must often procure a well recommended "app" that will truly erase all of your personal information. Additionally, and ideally, you should maintain control of your micro SD card and/or SIM module and not include these as part of the exchange of your old cell phone. Hi-tech criminals are not stupid and they are extremely motivated to pick up, on the cheap, old smart phones that were once state-of-the-art in their day, and will actively use all of their powers and tools to retrieve bank information, credit card information, and any other compromising communications that they can successfully monetize.
The consumer must recognize that when he relinquishes his cell phone without adequately obliterating his personal data, he may well also be relinquishing a pathway to identity thief, personal embarrassment, or even worse.