Currently I am using Ajax for map pulls. It will be a click and explore type map with no character to have to move around. You see something on the map you want to explore you click on it. A mini game pulls up.
Now for some math. Each map is a 600px wide x 400 px wide pic of terrain with dynamically placed objects characters can click to explore, harvest, or visit. The average map will have 10 clickable objects.
Each zone currently has 3600 maps. That's 36,000 objects. With my method of database storing and querying it will still only be 3600 entries per table.
I have mapped out 12 zones. That equals 43,200 maps and 432,000 objects. All except player built objects and the locations of interest will be dynamically built with code so I will be able to create these objects with no time.
That's 25,920,000 pixels wide X 17,280,000 pixels tall of map. If you were to visit every map for at least 10 seconds it would take you 120 hours or 5 days straight.
Now I am sure when reading this you are saying whoa! Way to much on the database, but it is actually not that bad. After the entire world is built with objects, places, ect... the actual map will only be 12 tables with 3 fields and 3600 entries each. 43,000 entries in a DB is cake, especially when broken up among several tables. The query to pull a map is very small. I can build a map with one pull of one field. I have a DB I use at work that has over 150,000 entries in one table and still works great.
Now the next question is Holy crud who wants to travel that far!! Well don't worry that's what vehicles are for

If I can pull this off this will be a extremely large game. Massive indeed. i am basing it off of the original FS where players built basically the whole world but in this version the world will still have hundreds of NPCs and NPC build towns and areas. Players will be able to add on and build their own towns and cities.