Tesla’s value plunged $10 billion in the past week to hit an 18-month low on Oct. 8, after the auto manufacturer’s CEO Elon Musk mocked the Securities Exchange Commission (SEC) with a sarcastic tweet and a major short seller compared the electric car company to Lehman Brothers before the investment bank failed.

Musk tweeted on Oct. 4 that the “Shortseller Enrichment Commission” is doing “incredible work’ and described his new nickname for the SEC as “so on point” after the agency required Tesla Inc. (NASDAQ:TSLA) and him each to pay $20 million in fines that will be distributed to investors the agency claimed were harmed. Greenlight Capital President David Einhorn, one of Tesla’s most vocal short sellers, pushed Tesla’s share price down on Oct. 5 with his investment firm’s third-quarter update that called Musk’s behavior erratic and blasted the auto maker for “deceptive” actions that will “catch up” with it, just “like Lehman.”

Tesla’s value has taken a beating in recent months, following several controversial tweets from Musk, his public podcastappearance in which he smoked weed and drank whiskey with comedian Joe Rogan and a lawsuit filed by the SEC prior to a Sept. 29 settlement that also required him to step down as the company’s chairman.

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Paul Dykewicz, www.pauldykewicz.com, is an accomplished, award-winning journalist who has written for Dow Jones, the Wall Street Journal, Investor’s Business Daily, USA Today, the Journal of Commerce,Seeking Alpha, GuruFocus and other publications and websites. Paul is the editor of StockInvestor.com and DividendInvestor.com, a writer for both websites and a columnist. He further is the editorial director of Eagle Financial Publications in Washington, D.C., where he edits monthly investment newsletters, time-sensitive trading alerts, free e-letters and other investment reports. Paul previously served as business editor of Baltimore’s Daily Record newspaper. Paul also is the author of an inspirational book, “Holy Smokes! Golden Guidance from Notre Dame’s Championship Chaplain,” with a foreword by former national championship-winning football coach Lou Holtz.