"Expert hacker"? I think not. ^^ 

A secondary source file can still be read easily 
by downloading and saving to disk from a select 
browser or two.

Prevention with right-click? Absolutely not, 
because someone need only to temporarily disable 
their browser's Javascript. Not to mention it 
would piss off a good number of users who use 
right-click to navigate (back, forward, bookmark).

Oh, I'm sure some people are familiar with 
something called "screencapping" - TONS of 
software to do that, all they have to do is have 
the browser open to that image.

Another thing, if anyone has their browser set up
remotely near "default", ALL downloaded images 
end up in the browser cache which can simply be 
viewed at leisure off-line. 

Basically, if someone can see the image on your 
page - THEY ALREADY HAVE IT. 

Now, before some fool yells at me for "releasing 
potentially damaging information" -this is for 
your own good. To know how someone can attack your
material is to know how to prevent it. But, the 
bottom line is, if you don't want someone to 
*have* an image, DO NOT PUT IT ON YOUR WEB SITE. 

I suggest all readers interested in protection 
and in watermarking or stamping search the 
archives for those terms (watermark, branding, 
etc.) This has been discussed at great length 
before.