Fair enough: if you are a company that is hiring and you have LinkedIn, then it should be your first port of call; if you have paid for it (or even the free version) then why not use it and save yourself some money. However, it is not the only method of sourcing candidates, and reliance on LinkedIn as your main method will seriously limit your exposure to the potential market.
Despite the massive growth in usage, many potential candidates are not on LinkedIn, and of the profiles that are on there, many are very outdated, or have very limited information.
There are other limitations: LinkedIn spamming is an issue – you can use Inmails, but the most sought after job seekers get a lot of Inmails, and most are ignored; unless you can come up with a very compelling message and hit the right person at the right time.
Don’t get me wrong, some companies are using LinkedIn very effectively to build relationships with candidates, but in specialist areas, good recruitment companies have got much wider networks and better accessibility to target candidates, even on LinkedIn. Good recruiters will be connected with many hundreds and often thousands of candidates, giving them a very wide reach.
Search consultants also have good researchers (either in-house or external) who provide an added level of expertise that is difficult to build in an internal recruitment team.
Not much has changed: twenty years ago, it was “We don’t need to use a recruitment company, we can place an advert in papers!” Plus ça change, plus c'est la même chose....