I'm not a specialist, but you can start by researching how the Opera company makes money. It would seem to me a possible future "catch" would be that they could charge selected advertisers to let their ads through...

From their own FAQ: http://www.operasoftware.com/press/faq

    "How Opera makes money"
    Opera provides cloud-based mobile services and
    solutions to operators, publishers and advertisers
    and enables hundreds of millions of consumers, via
    the Company's global cloud infrastructure, to
    connect to the internet content and services that
    matter most to them. Along those lines, Opera has
    different revenue models, depending on the
    customer type:
    
    *Operators.*
    Opera's revenue sources from this
    hosted solution include active user fees, data
    fees, NRE/development fees, hosting services,
    advertising and maintenance, and support.
    
    *Mobile consumers*
    (via partnerships with search
    providers and advertisers). The primary driver of
    mobile consumer revenue is revenue from mobile
    search, the Opera Mobile Store and active user
    growth.
    
    *Mobile publishers and advertisers.*
    Revenue comes
    from Opera's mobile advertising services and
    technology solutions, offered to premium and
    performance advertisers, ad agencies, publishers
    and developers.
    
    *Device OEMs.*
    Revenue comes through license
    agreements with a wide range of
    consumer-electronic-device OEMs.
    
    *Desktop consumers.*
    Revenue comes primarily from
    search and e-commerce partnerships.