The e-signature company DocuSign (DOCU -1.96%) has been a hot stock, appreciating over 40% over the past three months. That coincides with a broader tech stock rally, but there could be some underlying fuel to DocuSign's rise. Rumors are swirling of a potential buyout. This could mean that investors are bidding up the stock in anticipation of a deal being struck at a premium to its current valuation. That makes the stock more speculative, and should give investors pause before jumping into Docusign with bot ...