I usually would agree with chechu and djr33 on this one however, with the IE image toolbar there are two other considerations. One makes it fine in in my opinion to disable this feature. That is the fact that this image toolbar pops up whether the user wants it to or not, whether the designer wants it to or not. To many, it is simply unsightly looking. Because of that, I say, "Go ahead, get rid of it."
Fortunately, this feature is no longer switched on by default in new installations of IE. This stopped somewhere during the last year(s) of IE 6 and, as far as I know, is no longer used in the default config for IE 7. IE 7 installed on a computer that had the feature turned on in IE 6 may get it by inheritance.
Then there is the other consideration. Unfortunately, the easiest method for disabling this ugly 'feature' from the design side (the meta tag) also will create one of the many dreaded IE memory leaks. To avoid this, it is necessary to use the more tedious method of switching off this 'feature' which is by giving each image that displays the toolbar the attribute:
This is less tedious than one might think because images below a certain size never exhibit this toolbar and also some that are dynamically loaded to the page do not either. For wc3 validation junkies, don't even ask, of course it is invalid.
<img src="whatever.jpg" galleryimg="no">