Slack rocketed as much as 32% higher on Wednesday after Dow Jones reported Salesforce.com is in talks to acquire the workspace-communications company. Such a deal would likely value Slack at more than the $17 billion market cap it held before shares jumped. There's no guarantee the talks will lead to a takeover, and Salesforce could target another company for an acquisition, sources familiar with the matter told Dow Jones. The corporate-software company is in talks to buy Slack, Dow Jones reported Wednesday, citing people familiar with the matter.