Should You Run More Than One Company?It may sound masochistic, but these founders have found success with parallel entrepreneurship.

Jaclyn Johnson didn't set out to run two startups at the same time. In fact, she never planned to launch one.

The first came from necessity. At 23, after an unexpected layoff, Johnson took on freelance marketing projects to pay her bills. When her workload got big enough, she formed No Subject marketing agency, counting L'Oréal and Microsoft as clients. And there it was: company #1.