The Mobile Broadband industry is a very competitive one. Each year the big broadband providers try to bring out better deals in order to convince new consumers to sign up with them. Some offer free laptops others generous download limits. Three has decided to offer a new one month only contract aimed at those who don't want to get tied in to 18 months worth of monthly charges.
Their pay as you go mobile broadband offerings now include a month-by-month contract with a 5gb download allowance. Their 'dongle' (don't you just hate that word?) costs £20 on this contract taking the first monthly cost to £35. Users can cancel at any time and will only be required to pay for the remainder of the month. In contrast those canceling most 12+ month contracts are obliged to pay the remainder of their monthly costs making it effectively impossible to cancel most mobile broadband contracts.
This deal is likely to appeal to those needing mobile broadband in the short term. Students who spend part of the year at home will be able to use mobile broadband whilst at university without having to pay for it year-round. The downside to this plan is that you would receive a considerably smaller download allowance than with a long term contract.