Nowadays nobody bothers, but the online auction space was very attractive for a lot of people.
ebay still has a lot of flaws but the name is a verb for selling something online. You don't see many people trying to take them on anymore.
Being a big fish in a small pond can be profitable - these days, its Groupon clones setting up outside the US. I think this stands a higher than average chance of working - simply because the model does require direct interaction with businesses, and therefore local operators are going to have an advantage in terms of cultural/local knowledge.
If you're lucky to win your local market, you'll probably end up getting acquired by Groupon itself.
It is a valid strategy to get in and own a regional variation before the bigger players move in. But you have to move very fast - so fast that the 'big' player hasn't really been noticed yet, or bothered with the local market.
There's still plenty of countries with no real craigslist implementation. But for some reason nobody seems to want to do it.
So you're correct, you can early-move-copy on a big idea, but you've got to have the conviction to move early, and your idea must have ties to the locality through real life goods and businesses (or, I suppose, languages).