Some images I upload with FTP because they are old and they are generic type images...
I insert them into my posts with href="/images/thisone.jpg"
On the same post i will often link to a remote image and use Hot Linked Image Cacher to pull the image to my site and store it.
the plugin Hot Linked Image Cacher will choke on my local images because it does not know how to handle a relative url /images instead of http:/
It makes no sense for me to continuously upload images that I will reuse again and again... and the wordpress gallery is not built to handle lots of images... it is easier for me to look at my local directory on my computer .. find the image and use the /images/sub/subsub/subsubsub/imagename.jpg then to roll through page after page of images in a gallery... however please do not suggest NextGen.. it is also more time consuming then finding the directory on my computer that matches the directory on my webserver to insert relative image urls.
with that said ... what needs to happen is an edit that will overlook urls that do not start with http:// because relative urls are pointing to images that do not need to be redownloaded and cached on the server.