To know whether it's reasonable, you need to know not only the amount of revenue but also the revenue growth rate. I don't have the numbers in front of me, but my impression is that LinkedIn's revenue growth, while substantial, is not in the stratospheric territory that Google's was.
(There's profit to consider too, of course, but the business models of these two companies are similar enough that one would expect them to have similar margins.)
(There's profit to consider too, of course, but the business models of these two companies are similar enough that one would expect them to have similar margins.)