This is purely a matter of visual cognition - if the visual design makes it easy to group related elements, there is no problem putting anything anywhere, including buttons on a tab space. So long users can interpret the tabs as tabs and buttons (or other elements) as such, there shouldn't be a problem.
In the top example, the distinction is fairly clear - the visual features of the tab handles make them distinguishable from the buttons.
This is not the case with IE, where not only there is similarity between the tab handles and the search box, but also the tabs are positioned in between other elements making their nature less obvious.
Neither examples do well in terms of colours - ideally the tab handle and the panel will have the same colour so the two are visually grouped.
An example of good visual design for this can be seen in chrome:
The tab handles are highly distinguishable from the title bar buttons (minimise, etc.), new tab button, and the full screen button.
I can provide some reference to gestalt principles and additional visual examples.
But to answer your question directly - it is "OK" so long the visual design is not confusing (and it should be fairly easy to make it so).