Short seller Andrew Left is going after Facebook

Andrew Left's latest target is Facebook.

According to CNBC, the activist short seller with Citron Research is betting against the social network because it "is losing an extensive amount of relevancy."

Facebook is not a bad company, but it "just will not be a $330 billion company in a year," Left told CNBC.

Facebook shares fell as much as 1.6% in early trading.

This comes on a big news day for Silicon Valley as Microsoft announced it will acquire LinkedIn for $26.2 billion.

Left's most famous short remains Valeant Pharmaceuticals, which he called an Enron-like fraud. Since announcing the short position last October, and amid a federal investigation into its drug-pricing practices, Valeant shares have cratered 83%.