There's more than enough actions taken by Obama to Impeach him. Just like there was enough to Impeach Bush, and for the exact same reasons. The Senate would never convict though as long as the Democrats are in power. There would be some Democrat votes to convict, but not enough to get a two thirds majority.
Executive branch circumventing the Congress and the Constitution would be the reason, which is an Impeachable offense.
But, since Bush wasn't Impeached, Obama will not either.
Should Bush have been and should Obama be taken to task as well? Hell yes.
Will it happen? Hell no.
The Congress needs to take action, short of Impeachment, to prevent future Presidents from exceeding their Constitutional powers, and let the courts settle it.
Rand Paul, who I'm not big fan of, has taken one step to do just that which I do support, by suing the Obama Administration for that very reason.
But, since Reid and Obama are packing the DC Circuit with Democrat appointments, I seriously doubt that any legal challenge will succeed until we have a Republican President.