Once a company grows past a certain size, it becomes almost impossible for them to keep up with the mass of document shredding requirements. The amount of money it would take to have full time employee just managing and shredding all the documents which they are obliged to would be a huge waste. In order to avoid that problem, most companies now hire an outsourced paper shredding company.
Hiring a company to shred your paper does require some thought. There are many organizations out there which are now offering this service, and they are not all providing the exact same service. Certainly, they are not all doing so at the same rate, or at the same quality of service.
In order to be sure that you're getting what you need out of a shredding company, you want to only hire a company which performs on site shredding. This means that they will use trucks, vans, or other vehicles to bring their larger, fast paper shredders to your office's locations. There are other companies out there which want to take your paperwork to another location before it is destroyed, but this is not an option that you should opt for.
The reasons for opting for onsite shredding are several. First of all, you can be sure that you're getting your money's worth with on site shredding. If a company is charging you by time, not volume, and take your paperwork off site, you can't be sure if they're charging you a fair rate, or inflating their time quotes.
The chief reason to always hire on site companies though, is for security purposes. When a company takes your documents off site, there are many more chances for security or information leaks. The main reason that people shred documents is to prevent corporate liability. If you're letting a company take your documents off site, you are putting that entire goal in jeopardy.
Once a company is away from your location with your documents, you have no real proof of what they are doing with them. Even if they have signed a confidentiality agreement you have no idea if they are looking at the documents and potentially exposing critical information before they do so. You actually don't even know if they are shredding the documents or simply throwing them away as soon as they're away from your location. That might sound a bit extreme, but you can't really ever be too careful.