A paper published online in PNAS described a possible new form of regulation of gene expression by small RNAs. The authors found that small dsRNAs can also serve as transcriptional activators. They showed that the mechanism for gene expression activation also prefers dsRNAs of ~21 nt in size and requires the Argonaute 2 protein.
The story was covered by a news article in Science. From the news article it looks like there is some fear that the result might be due to indirect effects (inactivation of other genes leading to gene expression activation). Also, some wonder why this as not been picked up before by other studies.
I am very tempted right now to get some of the high-throughput screens of RNAi to try dig out some more examples that might have gone unnoticed (if I actually had any time to do it :).