MicroRNA or not microRNA?

The avalanche of next generation sequencing data has led to a rapid increase of annotated microRNAs in the last few years. Many of them are specific to individual species or rather narrow clades. A closer inspection of the current version of miRBase shows that dozens of entries conflict with other ncRNAs, in particular snoRNAs. With few exceptions, these cases show little similarities to canonical microRNAs, however, and thus they should be considered as mis-annotations.