What are some advantages and disadvantages for Yahoo of its boomerang hire program?

When Marissa Mayer became CEO of Yahoo, one of the first things she focused on was upgrading the company’s talent assets.
Because top technology talent is in such high demand, and because Yahoo’s declining performance had made it an unattractive employer, Yahoo was not having much success attracting top talent through conventional means. Mayer understood that many talented employees had resigned from Yahoo over the previous few years, and recognized that they could be very important to Yahoo’s talent turnaround and future success.
Yahoo also realized that, because hiring and developing new employees can take years compared to hiring back experienced people, it could be faster and more effective to reach out to ex-employees. Recruiters sent official Yahoo employee welcome packets titled “Yahoo! welcomes you” to ex-VPs, project managers, and lower-level engineers with the word “Back!” hand written after the title. The contents of the packet describe how much the company has changed under the new CEO, and how Yahoo wants to speak with the recipient about “big opportunities.”
The unorthodox strategy seems to be working. Within a year 14 percent of Yahoo’s new hires were boomerangs, or one in every seven new employees.