That's part of a larger discussion. When something is provided free online can the owner require me to view in a certain way. Network executives have described fast forwarding past commercials or even going to the bathroom during commercials as theft.
Likewise advertisers have claimed that popup blockers and Firefox addins that let users control how (and how much) of a page is displays are theft.
I don't buy any of that - if the page is availabe free of charge delivered to my house I should be able to view whatever portion I choose.
I am only aware on hotlinking cases that have been found to have merit in the case of pay content where the infringer was reselling the stolen content. Thats a crime no matter how you aquire the content.
That said, I don't hotlink except from major news stories or when I want to show that photo has not be 'shopped.
It cost me about $22 a year to run Boycottlasvegas.com at 1&1.com. That gives me 300000.0 MB a month so my cost for 2 meg picture is one hundreth of one cent (2 * 2 000) / (3 000 000 * 12) = 0.000111111111
And for that 2 megs a picture like this can be downloaded 57 time.
So thats half a million downloads for a penny. I can't feel too bad about that.