Well, just in case you don't:
(a) Tailgating Is Dangerous. Your vehicle looming in my rear view mirror distracts me. When you distract me, I'm less likely to react in time when something changes up ahead. And maybe I crash into the deer or bicyclist or car or toddler, and then you crash into me.
Not good enough? Well, try this one:
(b) Tailgating Is Counterproductive (at least, when you tailgate a careful driver). When I see you driving up close to my rear, I don't speed up. I slow down. And I'm not doing it to frustrate you -- at least, not primarily. The less room I have behind me, the more room I'll need in front of me. If I see an obstacle up ahead, and I slam on the brakes with you right behind me, you'll slam into me. The slower I'm moving, the more time I have to brake gradually before I reach the obstacle.
And if I slow down, you'll have to slow down. (Or pass me. PLEASE. But you could've done that without tailgating me first.)
So take a deep breath, and BACK OFF.