If the LinkedIn profile positively complements your resume, everything is wonderful. However, if your persona on LinkedIn is somehow different or adds confusion for a recruiter, you can be eliminated from contention for a job without even being aware of it.
Most job seekers create multiple versions of their resume because they have more than one objective in their job search, and/or decide to emphasize different elements in their background depending upon the specific targeted job. In such real-world situations, the static nature of the LinkedIn profile that is associated with these various versions of the resume creates a problem.
And, since LinkedIn currently gives no means to a person to create the equivalent of multiple profiles, one to match their different resumes/job targets, there is no satisfying solution.
With such an obvious inherent conflict, some people choose to make the LinkedIn profile all-encompassing, essentially a combination of all versions of their resume. Another approach is to use LinkedIn to supplement their primary job search objective, and lose the benefit of LinkedIn as a complement for the remaining career goals.
Either of these solutions is imperfect at best, and until LinkedIn allows for the equivalent of multiple profile functionality, there is no way for many job seekers to fully support their job search efforts using this otherwise excellent employment search resource.