I like the concept of taking "open-books accounting," as practiced by a growing number of businesses and NGOs, and bringing it down to the personal level - it's a natural relative of the open-source, sharing and open data movements, baked in for cooperative businesses and sustainable communities.
The trick is, as @bkad and other commenters have mentioned, that asymmetric privacy has different impacts on different people, and unilaterally disarming through financial transparency can change the power balance, not necessarily to the benefit of the disclosing individual. I've seen evidence that lenders and insurers are using the open web as data sources, not relying just on credit reports and data on application.
It's a big topic here yesterday and today at the sharing-economy conference in SF that PEERS is co-producing: Landlords and cities have strong genuine interests in protecting their investments and affordable housing long-term rental stock, and tenants and owners doing AirBnB hosting, and people taking action to meet their economic needs and share what they've got ahead of laws and clear agreements are suffering sometimes significant consequences, including 72-hour evictions and financial penalties.
Here's an example I witnessed in the past year, where transparency posed a challenge: at least one group of people creating community in this area got a late-in-the-process loan rejection because they were intending to collectively own a multi-unit property as an LLC and rent to themselves rather than to unrelated renters, and that didn't match the risk model of the lender, which assumed outside rental income; the bank may also have been anticipating that evicting/foreclosing on homeowners would be politically more difficult or more expensive/time-consuming than evicting renters after foreclosing on an absentee landlord. The group wanted to be open and welcoming and recruit partners to partners on their website, but couldn't afford to be if it means they couldn't get access to the necessary financing in the current market.
I ran into a similar issue close to home, and found a solution by stepping deeper into transparency, rather than trying to lock the barn door after the horse was gone: my neighbor couldn't get the federal approval needed for a reverse mortgage on her condominium because we publicly talk about our community as a cohousing neighborhood, sharing meals and common space, while retaining standard condo legal structure and financing. I launched a campaign with help from PEERS, lobbying HUD/FHA to change how it interprets rules. By shining a spotlight on the ways that we were normal, and showing that the differences were features, rather than bugs, we got over 10,000 signatures on a peittion over the first weekend, and found that change was happening before we even concluded the campaign and submitted the petition.
So if you are sharing numbers or other data that reveals aspects of your life, be aware you may be signing up for a life of radical honesty and only doing business with / getting access to capital or other resources from partners/employers/lenders with values alignment. Which could be a good thing, if you think about it, and the right direction for us to move as a society, but I do believe that we all should be able to choose how much we want to be a pioneer. Make it a conscious choice to push the limits of the system, and find ways to empower those around you so they too have choices in their lives.