Have you ever seen a motorcycle with a sidecar? By attaching a little car to the side of a motorcycle, you get the benefits of the motorcycle's size and open air travel and the benefits of a car's long distance comfort. Many site owners choose to do something similar by running Joomla and WordPress simultaneously. They want Joomla's flexibility and power in addition to WordPress's wonderful blogging capability. However, running these applications in tandem introduces several issues and, for a number of reasons, I recommend against using both systems together.