It is common to combine this account with your upload account. Make sure you have at least a few of these available. It will make you a whole lot more popular with other admins on the e-tree, and as a courtesy when you give yours out, you will usually get their mirror login in return. For permissions I like to give site-ops list and read access to everything, including the upload directory. Most site-ops know to check the MD5 file on a show before they host it, so you are fairly safe letting them download from your upload directory.
Most people give out at least a couple individual logins.
These are for people that do something really cool for you, like seed an ultra rare show to your site, or just regularly upload cool new material to your machine. To give them back a little something, you create a personal account for them so that they never get closed out of your site. This is totally optional, but if you operate a site for very long, you will probably give out a couple. You will have virtually unlimited access to almost any show that you care to find. You will get these shows first, since these days we are the roots that most trees grow out of.