People have long been saying that ethnic enclaves are a bad thing for society. As someone who likes controversy and debate, let me put my own alternative viewpoint into play: ethnic enclaves are good for society, and are just what society needs in this day and age.
In a global society, we need to encourage the free flow of people and resources to keep up economically. This applies to all countries. Protectionist measures are no good for the future of any country, and will be increasingly despised in this global world. A country's talent will need to be maintained and enhanced by immigration, or their industries will perish. A country also would benefit from having culturally diverse people as part of its workforce, and countries without this will not be able to keep up in the global race.
However, there is considerable fear from both natives and immigrants in every country, that their culture is going to be eroded. Nobody actually wants the world to be 'one culture'. For immigrants, life in the ethnic enclave is a way to participate in their new society, whilst not losing their cultural heritage. For natives, the fact that historically foreign cultures are kept in enclaves mean that the mainstream culture can continue its existence, whilst there are increased opportunities to make contact with different cultures, something which would have been the preserve of the rich just decades ago. It really is the best of both worlds.
A melting pot is a difficult situation for many people, as nobody wants their own culture to be melted down. However, we can all happily co-exist in a salad bowl, where nobody is melted down. Enough said.