The two sites that comprise Occupy DC -- McPherson Square and Freedom Plaza have remained long after many high-profile occupations across the country have been disbanded -- sometimes violently -- by police in riot gear wielding clubs, pepper spray, tear gas, and even flash grenades.
In January, Congressman Issa, who chairs the House Oversight Committee, wrote a letter to the Secretary of the Interior demanding to know why the National Parks Service had allowed D.C. protesters to violate a no-camping rule.* The letter explained that the McPherson Square had been recently restored, and the campers were damaging the grass.
Issa also called for a congressional hearing. After the hearing, National Parks (that is, the Obama administration) agreed to enforce the no overnight camping ban, but tolerate tents that were symbolic of speech and not used for sleeping. Any sleepers would be evicted from McPherson Square Park. (Incidentally, city laws don't prevent sleeping on the sidewalks as long as the sleeper doesn't pose an obstruction.)
Why was sleeping tolerated long after other Occupy campsites were disbanded? With the approach of an election year, the White House did not want to alienate a politically conscious group comprising many who voted for Obama in 2008.
It can also be observed that keeping Occupy DC alive, even as the administration gave nodding approval to the destruction of other Occupy sites, enhanced the prominence of Occupy DC. You can imagine how this might have served the interest of the administration.
"Occupy Wall Street" is as much a problem as an opportunity for the Obama administration. Wall Street has given more money to Barack Obama than any other politician -- Republican or Democrat. In 2008 Wall Street accounted for 1 in 5 dollars spent by the Obama campaign.
The genius of Occupy Wall Street was targeting the parasitic financial institutions that brought ruin to the economy and continue to suck the oxygen out of the American political system. OWS drew attention to grotesque income inequality; to the fact that an industry that provides few social benefits dominates politics and the economy. The Obama administration would surely have liked to have focused the energy of the Occupy movement into support for the Democratic Party, directing anger away from their Wall Street benefactors and towards the obstructionist politicians of the Republican Party (also in the pocket of Wall Street).
However, Occupy DC had been careful to target the tentacles of the corporate dominance. Protesters targeted the U.S. Chamber of Commerce, banks, lobbyists (McPherson Square is on K-Street). In spite of its proximity to the political establishment, Occupy DC remained true to the founding principle of the movement.