A soaring stock price doesn't always start with strong fundamentals.When a stock surges by more than 300% in a single year, it's usually because the underlying company is producing impressive revenue and earnings growth, or because it has secured a game-changing new deal with an important customer. But occasionally, the reason is far more speculative.Opendoor Technologies (OPEN +2.61%) stock opened this year at $1.59, and by June, it had plunged to$0.51. However, it has since rocketed to $6.70 -- not becau ...