Why is the USPS going broke?

  The USPS has not adapted appropriately to the changing times: they have adapted by charging higher prices for stamps.
  Of course, in the past if you were suspected of enclosing any kind of letter in a UPS box, you could get into deep trouble.
  And we all know how cheerful most USPS employees are. Try any post office that is not in a small town and you can pretty much guarantee you'll be standing in line for a really long time and when you finally reach your goal of the front desk with someone manning it who's not currently at lunch or "breaking," you'll be brushed off like an irritation. Smile not included.
  According to union contract, the USPS is not allowed to lay off or reassign employees; who figured that into the deal was guaranteeing that, in the light of email and so many more forms of communication, the USPS would not be able to sustain itself financially.
  Truthfully, you can't guarantee much when it comes to timeliness with the post office. 80% of their money goes to pay employees, while Fed Ex and UPS spend 32% and 53% respectively.
  One point of contention is this:

A particular irritant has been the yearly "prepayment" requirement for health benefits, mandated by the 2006 Postal Accountability and Enhancement Act to ensure that future retirees have coverage. USPS officials contend that no other government agency or private business faces such a requirement. Without that mandate, they said, the Postal Service would have turned a profit during the last few years.

  Options are being considered, according to the NY TImes:

In some countries, post offices double as banks or sell insurance or cellphones. In the United States, the postal service is barred from entering many areas. Still, the agency is considering ideas, like gaining the right to deliver wine and beer, allowing commercial advertisements on postal trucks and in post offices, doing more “last-mile” deliveries for FedEx and U.P.S. and offering special hand-delivery services for correspondence and transactions for which e-mail is not considered secure enough.

  The benefits of being a USPS employee are many, including these:

Full-time employees earn 13 days of vacation per year, increasing to 20 days after 3 years of service, and to 26 days per year after 15 years of service. In addition, postal service workers receive 10 holidays off each year. Finally, full- time employees are allowed to use up to 13 days of sick leave per year due to illness or accident.

 Salaries:

According to the APWU (American Postal Workers Union), an average postal worker's salary (Level 5/Step O) is $52,747. This salary has increased from an average of only $8,442 in 1969. 

  Judicial Watch reminds us of a few unpleasant facts about USPS:

Amid the crisis, Postmaster General John Potter, who retired a few months ago, received a six-figure bonus and his already-lucrative pay nearly doubled. While he threatened unprecedented layoffs and cuts in mail delivery, Potter’s salary increased from $186,000 in 2007 to $265,000 in 2009 and he got a sweet “performance bonus” of $135,000, bringing the total of his taxpayer-financed compensation—salary, bonuses, retirement benefits and other perks—to more than $800,000.
The USPS has also been marred by another scandal; of the hundreds of thousands of tax delinquent federal employees, the USPS has the most scofflaws with nearly30,000 workers who owe Uncle Sam close to $300 million.

  Cato also notes that it's difficult not only to lay off full time employees, but to moderate the rate of increases in compensation:

While the Postal Service negotiates with its unions to structure compensation, federal statutes hamper the USPS’s ability to craft market-based pay and benefits packages.27 The potential for mandatory arbitration gives the unions a big advantage in negotiations with management. When unions demand higher wages, more generous benefits, and added work rules, arbitrators usually give them part of what they want. And when weighing a decision on union contracts, arbitrators do not have to take the USPS’s financial situation into consideration. Not surprisingly, unions have been able to extract lucrative compensation packages from the USPS over the decades. 

The Government Accountability Office notes that the USPS covers a higher proportion of employee premiums for health care and life insurance than other federal agencies.28 USPS workers participate in the federal workers’ compensation program, which generally provides larger benefits than the private sector. Also, instead of retiring when eligible, USPS workers can stay on the "more generous" workers’ compensation rolls.29

  Apparently the financial condition of the organization is immaterial to the amount of the raise and benefit increase. 
  You can see here that not much experience is required to work for the Post Office. Score a 70/100 and you can get in. See here.
  You'll be happy to know there are 1143 positions available nationally, right now.
  So much for attrition.
  In March a contract was just settled; a congressional hearing is taking place tomorrow regarding pay, benefits, etc:

In addition to a 3.5 percent pay raise, the first 1 percent of which would take effect in November 2012, the agreement would protect APWU employees against layoffs and limit "excessing," where employees are reassigned to different work sites based on the agency's current needs. It also includes provisions that would return to postal employees work that had been outsourced, or assigned to managers. From 2013 to 2016, there would be a slight increase in employees' share of contributions to health benefits, totaling several dollars per pay period each year.

[snip]

Rep. Dennis Ross, R-Fla., chairman of the postal service subcommittee, said USPS cannot afford to pay employees more than their private sector counterparts, citing data showing that postal workers earn 34.2 percent more than comparable workers at commercial companies.

  So basically closing post offices and stopping Saturday mail won't make any difference when it comes to saving money since the USPS can't really lay off anybody.  
  Should be an interesting hearing tomorrow.