NEW YORK (TheStreet) -- Tesla Motors(TSLA) - Get Report dropped by 2.7% Friday, closing at 220.69, after the company's stock was downgraded for the third time this week.

Barclays analyst Brian Johnson downgraded Tesla shares to underweight, citing significant challenges ahead for the electric vehicle maker. His research report came on the heels of downgrades by Morgan Stanley analyst Adam Jonas and Baird analyst Ben Kallo.

Read the full report of all three downgrades and the challenges ahead for Tesla from TheStreet's Technology Editor Chris Ciaccia.

Separately, in an incident that could probably only happen in Silicon Valley, a Tesla Model S rear-ended a Google self-driving SUV in August, according to the California Department of Motor Vehicles, SiliconBeat reported Friday. The crash occurred in Mountain View, where Google is headquartered.

Google had publicly announced some details of the crash in September, SiliconBeat said, but the DMV has just released the previously unknown detail that the robot car was rear-ended by the Tesla vehicle.

Shares of Google's parent company, Alphabet(GOOGL) - Get Report  , rose Friday by less than 1% to $671.24.

EMC (EMC) jumped by 2.5% Friday, closing at $27.87, amid reports Dell is lining up a $30-per-share offer for the data storage company. Dell's bid could be announced early next week.

CNBC reported Friday that, according to its sources, Dell's offer for EMC would include cash and also a tracking stock for VMware(VMW) - Get Report , which is majority-owned by EMC. The entire package would be valued at $30 per share, CNBC said.

Read TheStreet'sfull report on why EMC stock moved higher Friday.

Shares of VMware finished the day at $78.66, a gain of 1.8%.

Dell, which was taken private two years ago, is stuck in the slumping PC market. Taking over a company like EMC could help it diversify and expand into more lucrative markets.

Shares of slumping GoPro (GRPR) bounced back by 5.4% Friday, closing at $29.08, a day after the company hit a record low. Morgan Stanley reduced its price target on the company's shares earlier this week.

GoPro shares have dropped by more than 50% in the past two months.

GoPro rose on Friday despite cautious comments from analyst firm Oppenheimer, which said it believes GoPro's average selling price peaked in 2014.

Read TheStreet'scomplete analysis of Oppenheimer's report and the challenges ahead for GoPro. 

Apple(AAPL) - Get Report shares rose by 2.4% Friday, closing at $112.09, amid reports the technology giant is increasing its share of the global PC market, even as other manufacturers experience declines. Read reports from MarketWatch and SiliconBeat here and here.

Twitter(TWTR) - Get Report  jumped by 1.7% Friday, closing at $30.84. The company is planning company-wide layoffs next week, Re/code reported.

Twitter declined to comment, Re/code said.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.