LINK. The general public will probably make the assumption that this is only a problem uptown but many other neighborhoods have similar issues. The top map was from a New York magazine story in the fall of last year and it lays out all the new gang activity in the NYC area: LINK. Hot nabes such as Willamsburg, East Williamsburg (AKA Bushwick), Fort Greene and the Lower East Side are also in the red alongside the area by pristine Morningside Heights.
What really matters here is working with the new DA's office since they seem to be making progress at mitigating gang activity on the specific blocks that have problems (thanks to new technology). We've seen a few petty crime complaints posted in the past but the police are definitely not reading blogs to find this stuff out so contact the appropriate offices to stop anything that might be illegaly happening on a residential block. Join the block associations, be active in the community board meetings or contact Linara Davidson from the Manhattan District Attorney's office for all concerns relating to youth gangs: email@example.com.