Firsthand Funds CIO and portfolio manager Kevin Landis told CNBC's "Closing Bell" that the decline in Twitter's MAUs is "uncharted territory for them."
"The product is essential for those who tweet. The product is not essential for those who simply check their Twitter feed," said Landis, who owns Twitter in the Firsthand Technology Opportunities Fund and was also a pre-IPO investor in Twitter, said.
On the revenue side, $710 million for the quarter represented a 48 percent increase against $479 million in the year-ago period.
Advertising revenue totaled $641 million, a 48 percent year-over-year jump, but less than the $647.7 million expected by Wall Street, according to StreetAccount.
Twitter also disappointed Wall Street on guidance, saying it expects first quarter revenue between $595 million and $610 million — analysts had estimated about $633 million, according to StreetAccount.
The social media company said it saw a 153 percent year-over-year increase in ad engagement during the fourth quarter, but it recorded a 41 percent decrease in cost per engagement (CPE) against the comparable year-ago period. Twitter attributed that fall to "the shift to auto-play video, which delivers more engagement at a much lower average CPE than click-to-play video ads."