So here's my 2 cents worth... I did a quick math on what's still at stake:

1.) So far Obama has a lead of  round about 120* PLEDGED delegates (I am not going to speculate on the so called SUPER delegates here).

2.) There are still 1078** delegates at play until the last primary in Puerto Rico is over on 06/07/08.

3.) There is still the wild card of the botched MI & FL primaries in play (potentially about 330 delegates, of which (and I am speculating here) if the results stand, despite the NON campaigns in those two states Clinton would roughly pocket 170 and Obama would receive about 116 delegates)

Scenario 1: 
FL & MI count and my figures are aproximately correct. This means that Hillary needs to win the remaining
18 states by an average margin of 6% just to EVEN out Obamas delegate advantage. This is the most optimistic scenario for Sen. Clinton, given the strategic difficulties in actually getting FL & MI counted the way she would liek to see it happen.

Scenario 2:
FL & MI don't count. In this case, Hillary Clinton would have to win the remaining 18 states by a whopping margin of 11% in average, just to DRAW the pledged delegate count with Obama.

It looks like even with the more favorable  scenario for Clinton, that this is becoming to be a steep uphill battle for her, unless the Obama camp gets into some serious PR trouble. Given his momentum he should round up the most pledged delegates by the end of th primary cycle.

Hillarys best bet seems to be, to try and get close to Obama's delegate count and the hope for the super delegates to vote her way.

*Numbers averaged from CNN, AP, CBS & RCP
** Source: RCP's delegate list.