Is it simple? Yes. Risky? A bit. Legal? We'll leave that to the lawyers 'cause we know that you're aching to give tethering a spin over your newly downloaded iPhone OS 3.0 update. We've seen several guides to enable tethering ever since OS 3.0 was first released into beta (and into the wilds) oh so many days ago. However, these were always carrier/country specific and required a bit more command line tampering than the common man could stomach. Now an automated solution has come to our attention that just works, is global, and doesn't require a jailbreak. Essentially, you use your iPhone to browse to a site that you've never heard of (help.benm.at), download a file that promises to reconfigure your local carrier profile, and then switch on tethering as you would had you tithed a monthly tethering fee to your carrier. We've confirmed that it works on T-Mobile NL and on O2 UK. There's obvious risk here so be careful and backup your iPhone first before giving this a shot. And don't go nuts either -- remember, your unlimited data plan likely contains a "fair use" clause and you can bet that carriers won't be happy to see their bandwidth diminish without compensation. Now brace yourselves and hit the read link for the full procedure... ready, go!
Update: Some are reporting that this procedure could disable MMS and visual voicemail depending on your country and carrier -- a fair trade for many.
Update 2: Techradar reports that O2 UK has responded to the tethering hack saying, "we reserve the right to charge customers making modem use of their iPhone or disconnect them." This assumes O2 can identify such customers.