Basically a reading list means you can subscribe to the URL of an OPML file, but instead of importing all the feeds in one batch, they kind of virtually exist in your RSS reader…if a feed is added or deleted to the OPML file, then this will reflect in your RSS reader…dynamic!…see my explanation.
From what it seems when you subscibe to the URL of an OPML file it becomes a folder in your RSS reader called a guide.
You can set the settings to how recent the reading lists update.
The problem of even loading static OPML files is the same, a feed may appear multiple times in your RSS reader (you may be OK with this, if not you are alerted for duplicates).
Even if you have duplicate feeds, once you have read it in one folder, it should automatically be read in the other folders.
Reason you may keep duplicate feeds, is that each of your feed folders/tags may have a spliced feed or an OPML file of their own (that you can share with others), so you may want a feed to appear in all these files…in fact if you have an OPML file for each folder in your RSS reader, this means that each one will be a reading list.
So now if you can share your folders or tags that contain feeds in a feed folksonomy like Rojo, this would make it a Reading List folksonomy. Other services like RSSor also enable you to collect feeds and store them in tags, if each tag had an OPML file, then this too would be a Reading List.
Not sure if BlogBridge users share their folders of feeds, but a good idea for BlogBridge would be to make their Expert topics OPML enabled so they can become Reading Lists…why not add in a spliced feed as well.
Some Reading Lists you subscribe to may not change that much, but there are Reading Lists that will be changing continuously, eg. PubSub’s Community Lists (these have an OPML file making them Reading Lists).
Since this list is based on influence, authority, popularity (basically on the quantity of incoming links) blogs will drop in and drop out all the time.
Same would apply to Technorati Top 100 (only if it had an OPML file…and only if this list was categorised, and these categories each had an OPML file).
Feedster Top 500 is nearly there, as the feeds are categorised (by user tags), all they need is an OPML file for each tag to allow for Topic Based Reading Lists, based on user tags, and incoming links.
If you just subscribed to Reading Lists from popularity lists in your RSS Reader, you would be reading the hottest blogs (most popular) in each topic (Reading List), and if a blog isn’t hot anymore (no one is talking about it or linking to it), then it won’t be in your RSS Reader…all done.
Now that you can subscribe to a dynamic continuously changing list of the hottest blogs, how do your read these posts, if you click on the Reading List folder in your RSS Reader can you read this list as a river of news, and what about ranking the items…see my post on OPML Sampler that can rank popular items in an OPML file.
So now you would be reading the hottest posts from a continuously changing list of hottest blogs all the time…now that’s hot!