A foot tattoo (a well done foot tattoo) can look absolutely amazing, especially with a pair of heels. Beware: it hurts like crazy, only for those who aren't afraid of pain (trust me, i have one).

It depends on the foot. I, personally, couldn't have one of the foot because my veins are too close to my skin and my feet aren't wide enough to have much options for images to place there anyway.

I think it's cute as long as you pick a good design and a good placement/angle though.

Easy to view if you wanted to, yet also easily hidable. The foot seems like it would be a hard canvas to use for an artist, so this probably limits you to a small tattoo.