Guys, let us brainstorm!!!
First, just a note - I'm not saying that I'm against such a feature, if you look in redmine you'll see that it is on the list, but I'm starting to more and more doubt the value of it. Of both - adding the hotspots to multiple categories and having subcategories.
When I'm on amazon, I have a specific goal - to buy a book. I don't start browsing the categories to find my book, I use the search box. So for me, it is HIGHLY important to have an awesome search box. A box that will understand when you search for a city, or a street and will move the map to this location and will show you everything available there. A search that will show you not only restaurants, but Chinese, Bulgarian and french restaurants.
As I was thinking about the subcategories yesterday, I thought that if I was to implement the following:
Marker icon - which means you could either use the default category icon for your marker, or you could use a custom one.
So when you post to a restaurant category, you could just select an icon for Chinese food and there we go - the users will be able to see the restaurant.
Additionally what would most probably really help is a tagging system.So you could have just the main categories, but your hotspots could all have the tag "something" and they could be searched for it.
I really don't remember when was the last time when I went to a website and started browsing trough the categories. Moreover - when I see 200 categories I just give up - there is so much choice! My brain gets overloaded and decides that it doesn't have the time for this shit.
Go over New York in google maps and search for coffee - how many thousands of results do you get? A lot, right? How many of them do you click? Most probably the ones that are near your location and the ones that are marked on the map with a big letter A, B, C, D....
You don't like pure coffee that much, so you want cappuccino? Well, I don't think that you'll come to the idea to go to a category coffee, than to cappuccino? Naa, you are just giong to type cappuccino and you get what you want - coffee shops that serve cappuccino as well.
Hiding your markers in a lot of categories and subcategories and publishing them in more than one category was probably working in the past. Now it is all about finding information fast, and browsing trough a lot of categories doesn't seem like the right solution for me.
Daniel
P.S. @eliecer - If I eventually come to the implementation of subcategories, I was planning to do it the same way as you outlined in your screenshots.
@preston - what about the duplicate content problem you are going to get with google and other search engines?