Some sites no longer rank well for long tail searches. This is due to a change in Google's algorithm. This change is here to stay.

Google has deliberately made this change to improve search quality.

If your site is affected, this is likely because your site ranked for a long tail keyword that wasn't entirely in sink with your overall site topic.

Make sure you keep the content topicality of your site consistent. This will help in maintaining your rankings for topical long tail searches.

Also read our blog post about Google's Mayday update for long tail searches.