3 UK is set to deliver truly unlimited mobile broadband, tethering included.

In the world of mobile broadband Internet, “excessive use” is a phrase that we’ve all come to be too familiar with. For the 1.5 million mobile Internet customers on 3 UK, that term just flew out the door. The UK’s 4th-largest mobile carrier has just introduced truly limitless mobile broadband packages, replacing the previous 1 GB cap for £25 plan.

According to what we’re reading over at the New York Times, the company is including tethering in the plan. The Times brings up the fair point that this could overwhelm 3’s network, which covers the vast majority of the UK population. However, it’s worth mentioning that the 3G speeds are certainly no substitute for a dedicated, broadband connection in the home.

Will this open Pandora’s proverbial box for other wireless providers in the UK? It’s not likely that we’ll see Vodaphone immediately drop its tiered, monthly-capped pricing scheme, but it does open the door to investigation. With the growth of 3’s network due to the merger of its network with T-Mobile earlier in the year, the move will certainly give the competition pause.

Putting it all into perspective, you can now walk into a 3 retailer, purchase an 3Phone 4 at £69, then pay £35 per month for 2,000 minutes, 5,000 texts plus “all-you-can-eat” data. That’s compelling, no matter how you look at it.