Job-hopping is pretty commonplace in the modern day, particularly with younger generations. It used to be seen as an entirely negative thing – the candidate is non-committal, they won't stick around so they won't worry about the standard of their work, they're only here because you pay more than their last employer. However, times have changed and recruiters are starting to see the positives.
For starters, job-hopping applicants often have a broad range of skills and experience. They've probably moved from company to company, both large and small. They'll have picked up soft, transferable skills as well as more industry specific ones, and they'll have knowledge about how competitors operate. It's 'career-hoppers' you should be wary of, those candidates who have never settled in a particular industry.
Job-hoppers are also quick to adapt because they've had to. When you move from role to role, you're quicker to assimilate and quicker to take to new tasks and responsibilities. That ability to adapt makes them an asset.
Another valuable thing job-hoppers often bring is a wide business network. They will have contacts and will know people who know people. That can come in handy if you're looking to outsource a task, or want word-of-mouth recommendations when filling a vacancy. Always go for job-hoppers who can provide as many references as you like. Those without references probably also lack the network.
Finally, they almost always bring enthusiasm. When someone has been in a job too long and the honeymoon period has ended, they can lose motivation. Those who switch and take on a new challenge tend to throw themselves in with real passion, and that's what you need.
They have a wide range of skills
They have plenty of industry experience
They are quick to adapt
They often have a wide network
They tend to have more enthusiasm