The coming departure of Salesforce.com’s platform chief Tod Nielsen highlights a stark problem for the company. After years of effort, it’s been unable to unify its two platforms for developers building apps in the cloud, Force.com and Heroku. And that is leaving it vulnerable to growing competition from Microsoft, Google and EMC in the enterprise cloud market.

Though the app building platforms are a relatively small part of Salesforce’s $6.7 billion business now, the stakes are high. The race to court enterprise developers in the cloud—that is, the coders inside big companies that write their apps or the software firms that target these big companies—is one that Salesforce needs to win if it hopes to keep growing and reach CEO Marc Benioff’s stated goal of $10 billion in revenue.