What do starbases do? I had some around a few planets pretty well equipped and the enemy still invaded teh planet without the starbase firing a shot. WTF!! What good are they?
Military starbases, I take it? They don't do anything on their own- you need ships in their area of effect. Friendly ships will get various enhancements, enemy ships can be slowed down slightly. If you want to defend a planet, you'll need some ships in orbit. Just don't confuse the ship assist modules with the starbase fortification modules, as the former will grant bonuses, while the latter will just make your starbase a very expensive decoration.
The main starbase used near planets will usually be of the Economy type- they add a percentage on to the production and research of all planets in their area of effect. Like all starbases, their area effects stack, so you can get some absolutely ludicrous enhancement levels going. I use them for my main research and production planets- several thousand units per turn is entirely possible.