Legal: It will be hard to argue in court that you have right to create fake accounts. That is definitely against TOS, and at that point Linkedin can sue the company instead, so I believe it would scraper would not be successful at court.

Technical: This is actually what you want, as limiting scraping per user is easier than per IP, since IP can be shared by users, so your rate limits have to be higher for IP address than for individual user. Additionally, creating fake account is more work which will in the end making scraping more expensive.