Look at Recruit’s existing line of business and revenue. The bigger question, to me, is what happens if Google decides two sites dominating their organic listings is not welcome.
Massive backlash, claims of bias, lobbying and negative PR pieces, and more than likely regulations would then follow, putting at least a sizeable damper on their business and an unforeseen impact on future business. Companies with millions of dollars available to them will not go down without a fight.
So froogle/shopping.google all over again? I think Google made the change in 2012[1] with no meaningful backlash in the US and a fine in the EU they are appealing. So I think the lesson is that Goog can do whatever they like with job searches.
