Based on their landing page source:-
<!DOCTYPE html>
<html>
<head>
<style type="text/css">
html, body, iframe { margin: 0; padding: 0; height: 100%; }
iframe { display: block; width: 100%; border: none; }
</style>
<title>Application Error</title>
</head>
<body>
<iframe src="http://s3.amazonaws.com/coinbase-public/error.html">
<p>Application Error</p>
</iframe>
</body>
</html>
And the error.html:-
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Coinbase Error</title>
<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.0/jquery.min.js"></script>
<style type="text/css">
body {
padding: 50px;
}
</style>
</head>
<body>
<div class="container">
<div class="row">
<div class="span8">
<p><h1>Coinbase Error</h1></p>
<p>Whoops! It looks like we encountered a problem.</p>
<p>We've been notificed about the problem and are working on it. Please try again in a few minutes or you can <a href="https://coinbase.com">return to the homepage</a>.</p>
<br/>
<h4>We'll post updates on Twitter if the problem persists.</h4>
</div>
</div>
</div>
</body>
</html>
It seems more likely that they're having an error, than have 'stolen your money'. A little trigger happy I see? God. How long have they been down for you? Five hours, maybe? That was their last twitter post. Give them a little time to fix things, computers aren't perfect.