A lot depends on what the objective is......IF it is to delegate the complete hiring activity/process to another person & you focus on other tasks, then that stage would come only much much later.
As a thumbrule, until you build-up the company where there are at least 2-3 tiers between you & the level you need to hire/interview, you WILL have to participate in the hiring process. I know of companies where the CEO still meets....even if for 5 mins......every hire [despite there being ~5-6 tiers between him & the bottom-most level] to give a psychological impact to the hiree. In the long-run, this is quite important for any Company.....big or small.
There's also another reason why it's imperative that you excuse yourself from the hiring process 'as the last resort': A wrong hire will be far more expensive for the organization than a delay in filling any position.....if you find it tough to spare time to participate in interviews. As a Founder, the buck always stops @ your desk.....be it a bouquet or a brickbat.
Like Fernando mentioned, Hiring is a crucial function.....especially until the scale is reached.
Delegate the coordination activities [thru RPOs, Agencies, etc] IF you wish to save your time.......but NEVER delegate the decision-making until you reach the critical mass--obviously goes without saying that this means that you really can't distance yourself from the hiring process for sometime to come. If that's telling on your precious time, it would be better to find other ways to handle the situation(s) than cutting your involvement in the hiring process.