It depends on what your site is worth and how much traffic you are driving. If you are Google, it's a no brainer. If you're getting 1k uniques/mo, it's a need

It depends on what your site is worth and how much traffic you are driving. If you are Google, it's a no brainer. If you're getting 1k uniques/mo, it's a needless expense. The tipping point lies somewhere in between. My guess is on the high end, but I have little evidence to back that up.