In this day and age, it is very easy to find someone to create almost anything for you or your business at the mere click of the mouse; however, what most people forget when they make that easy hiring decision: paying for the work does not mean that you OWN what was created--it merely means that you have the right to USE what was created.
In other words, if someone hands you work that he or she created and no copyright assignment is made, then you typically are just going to receive a nonexclusive license to use the work created. However, if the license is not written, then the extent of your rights is technically unclear and not actually defined. Thus, your license could be terminated at any time.
So, what does this mean? It means that if you decide to repurpose the work that was created and use it in an alternative way, i.e. other than what was contemplated by the contractor, then you may be committing copyright infringement. Similarly, if you decide to create a derivative work of the original work which was created, well then you may be commiting copyright infringement as well, since only the owner of the IP in a work can authorize the creation of derivative works.
In the current economy, I see this issue come up quite often in terms of payment disputes. The buyer of the work decides not to pay the invoice for the work that was created but wants to continue using the work. Obviously, if you only have a license to use work and you breach that license by not paying for the work, then you are technically infringing the copyright of the creator if you continue to use the work after the dispute arises.
Thus, the best practice when you are hiring someone to create something for you--whether it is artwork, text, videos, designs, software code, music, or any other type of creative work--is to make certain you get a copyright assignment from that person BEFORE you pay him or her any money for his or her work. And, if you have a payment dispute with the person you hire, you need to resolve that dispute and you should stop using the work until a resolution has been reached which involves an assignment of copyright. And, of course, it's always best to discuss your expectations with this person when you hire him or her rather than after he or she has already finished the project, as he or she is always going to be more willing to enter into a copyright assignment before starting the job rather than after the work has been concluded.