It makes sense -- after all, part of Instagram's success hinges on the ubiquitous use of hashtags and how easy it is to find new-to-you users. This move helps individuals connect more fully with the hashtags they contribute to, as well as with other accounts they run (or accounts of friends and family) on the service.

If you do link to someone else's account, that person will receive a notification. They then have the option to remove the link from your profile. It's a good security measure that will surely cut down on abuse of this feature.