I've tested the plug-in by creating more than 20 markers/posts. With that many identical markers on the interactive map you need help to find the data you are looking for - and clicking on each individual marker and reading the text is a no go.
So in order to help readers/contributors filter the data I have assigned the posts to different categories and given them descriptive tags. This enables the reader to easily access the data belonging i.e. to a specific category.
But when you click on a category and go to the page listing all posts belonging to the category (category archive) the posts contain no location-data/map. This also applies to the tags archive page. This unfortunately makes the lists pretty useless.
In regard to filtering data it is also problematic that the text entered in the field "Title" on the form a contributor fills out in order to place a new marker on the map, automatically creates a new category. Contributors will create individual titles and most likely write a headline. So you could end up with an endless number of categories each containing only one post.
I believe contributors should be able to write a headline of their own choice when posting/adding a marker. But the headline should not generate a category. A valueable addition to the form contributors fill out would be a field with a menu that lets contributors choose between a limited number of admin-generated categories. That would enable a filtering of data and improve the usability and scalability of Sightings.