Opendoor Technologies, a penny stock last week, attracted sudden interest among Reddit-obsessed retail traders, who pushed up the stock price by threefold in days.The online real estate startup saw shares popping more than 14% Tuesday,

The online real estate developer's shares are on a stellar run. Investors should be careful not to get burned.

Opendoor's stock is coming back from the dead. The real estate platform has struggled to scale and cannot generate a profit. A flawed business model should keep investors away from this stock. Animal spirits have returned to the stock market in a big way.