Not that it is a massive deal... I guess I just got in the habit when I was younger. Like I said, I always used import_request_variables (with various prefixes).
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But back to my question - is it bad to use like I have?
echo $blah; // hi <script>alert('foo');</script>
Second: it will double the memory used.
Third: you can't use the variables global anymore
Good point on the memory, but I wouldn't think thats a big issue. I haven't tested right now, but I dont remember ever having issues using the $_GET variable after exporting? Not sure if thats what you meant.
I can't immediately think of a practical way to make a problem out of that. But, you're making a couple of bets here: you're betting that there never will be a problem with it, and you're betting that the rules in PHP won't change in the future. All those folks that relied on magic_quotes already got boned by that second bet.
So, no, I wouldn't do it that way, but I wouldn't criticize you for it either.
$blah = "hi $_GET[hello]";