Twitter shares were trading at $70.21 seconds after the open, down 4.23% from Thursday's close of $73.31.
Shares of Twitter have nearly tripled since the social media site went public at $26 price on Nov. 6, and Schacter sees no justifiable reason for the run-up.
"We continue to believe that Twitter as a company has a bright future and many opportunities ahead," the report states, according to Bloomberg. "However, as a stock, we believe nothing has changed over the last 15 days to justify the rise in valuation."
Following the downgrade by Schacter, eight Wall Street analysts have "sell" recommendations on the stock, compared to seven "buys" and 12 "holds." The wildly hyped and widely used site has yet to turn a profit, but some institutional investors see it and Facebook (FB - Get Report) as the only obvious ways to invest in social media.
Facebook shares have more than doubled in 2013 and are up just over 14% since Twitter's IPO. They trade at about 120 times earnings versus about 20 times earnings for the S&P 500.