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I'll do selective sharpening on those borderline sharp images, usually just on the main focal point. There is one site in particular that is very picky on image sharpness. Without sharpening a little the image would never get accepted.   

If you used a tripod and remote  switch you would not get "those borderline sharp images" IMO.
Even with  an image stabiliser built in to a lens you may still get camera shake if you don't 'hold' that shot for a few seconds.

I shoot everything hand held, prefer to work that way. I might be a little pissed off when the next wave comes in and takes out my tripod, camera, and leaves me holding the remote.  I hear what your saying though. I do use a monopod on occasion.

It happens 

I dont sharpen every single image, but most of them. The big thing is if you are going to print a digital image...then it definitely needs to be sharpened.

sharpening is USUALLY the last thing to do to an image, indeed. Most of the time - selective sharpening. in 90% of the cases the only sharpening I do is in LightRoom in raw workflow. If the image is slightly OOF then I'm using some cool plugins...
But in more than 90% of cases there is no sharpening needed.
I have a 5D.

Don't you usually downsize shank? That has a sharpening effect, especially if you're using the bicubic sharper algorithm to do the downsizing.

It depends on which lenses you are using.
For macro work, you don't need any sharpening since macro lenses are the sharpest.
Most wide angle lenses are not sharp, especially on the borders, and you might need to apply some mild sharpening.
It also depends on size. The smaller the size the more sharp it looks.
It varies on a photo by photo basis.

I do light selective sharpening by the supersharpen workflow (the Miz described it) in the lightness channel alone (convert to Lab colors) in a layer under the original.
If it's a landscape, I set the opacity for the original on top to 80%, but only for the land part and avoiding smooth gradients like sky and clouds where the added noise will be most visible.

For portraits, I use a soft erase brush 15-20% on the eyes, lip cracks and the nose opening (points of attention focus). Vonkara: on an isolation, never sharpen the borders to white of course. After flatten layers, I zoom in 600% (yes I'm a stupid pixelpeeper) and I blurr the single black pixels here and there with a soft brush 2px. The eye white gets blurred a little bit too with a larger brush.

I'm always puzzled by a rejection for pixel distortion. When I zoom in at 800%, they all look perfectly square to me 

Well next time put your tampons on and climb the rock and it wont be so blurry

I sharpen probably 99% of my images.  I only shoot raw and at least one (though usually two) runs of the Unsharp mask does the trick.  Granted, my work flow is not very practical...I do all my RAW conversions in Lightroom then open all images in PS for final tweaking which includes sharpening. 

I never sharpend an image... even if I use my crappy zoom-lense