Widmore is on Jacob's side by nyoe_Shephard

This is a very important question, however, I'm not going to spend a lot of time answering it. I'll keep it short and sweet. Ben's quarrel with Widmore began when he exposed Widmore's affairs off island with an anonymous woman, and banished him. Widmore wanted Ben Linus dead, and Ben knew this. Ben, pretending to have orders from Jacob, notified the Losties that Widmore is off island, on a freighter, with only one intention: to kill all of the living people on the island.

This is false, we don't now Widmore's intentions, but Widmore was only there to kill Ben. We know now that Ben had not ever even seen Jacob, he lied to gain power. Therefore his input on whether or not Widmore was a bad guy was very skewed; he would do anything to convince the Losties that Widmore was an opposition so that he could have their trust and protection to keep him away, because he knew Widmore was coming for him.

Widmore is still on Jacob's side, as was every other Other on Ben's team. Locke is going to want Widmore dead for obvious reasons: kill or be killed.