USSD code to factory data reset a Galaxy S3 can be trigged from a HTML page
Here's a safe version of the exploit that displays your IMEI:
<a href="http://kristofferR.com/samsung.html" rel="nofollow">http://kristofferR.com/samsung.html</a><p>Check the html in your desktop browser first, for all you know I might as well be a malicious douchebag.<p>The exploit seems to require a stock Samsung Galaxy dialer, works fine on my cheap Samsung Galaxy Y but not on my friend's modded S3 with a vanilla Android dialer.