Luckily, there's an extension which fixes this:
https://chrome.google.com/webstore/detail/reclaim-backspace-...
I'm an avid backspace-as-back user, so I went searching for a solution as soon as they introduced focus-stealing.
I would expect the opposite behaviour to be annoying though, I've "lost" searches by hitting backspace and unexpectedly going back when I thought I selected the URL bar and waited to delete what was inside. Try to use alternative shortcuts rather than the overloaded Backspace.
I'll search for something, decide to go back, and now I'm deleting my search term instead. And the fact that Google searches based on what's in my search box (without having to hit enter) I've actually "lost" search results that way.