American investor Reuben Kressel, 66, has sold his entire stake in Twitter Inc. on Friday morning. Kressel bought 500 shares of Twitter earlier this month when the stock was priced at $52 apiece.

Kressel told the Wall Street Journal on Thursday that he would dump his Twitter shares when the price dropped by a couple of dollars. Sure enough, Twitter shares dropped as much as $5.91 of 8% on Friday, after an analyst downgrade raised valuation concerns about the stock.

Kressel's move illustrates the fickle nature of many retail investors who have piled into Twitter during its 182% rally since its initial public offering in early November. Some are true Twitter believers, while others invested to make a quick buck. Retail investors could bail on Twitter just as easily as they gravitate to it, the report said.

Macquarie Group analyst Ben Schachter said he expects other analysts to adjust their views on Twitter in the coming days and weeks. Schachter downgraded Twitter shares Friday morning on valuation concerns. WSJ, citing Thomson Reuters, said that nineteen of the 26 Wall Street analysts that cover Twitter have the equivalent of hold or sell ratings on it.