If Baidu buys Qihoo (unlikely), it'll be a DROP for Baidu, initially. Keep in mind that Qihoo is a minute fraction of Baidu's business, so a buyout would not be a valuable investment right now. Better to let Qihoo run with their ball for 9-12 months and see what business they drum up. Then, if they truly become a meaningful business entity, it would be a wise purchase.
Actually, i have to correct myself. Qihoo's doing pretty well, and their net is better than i had seen a while back. So, maybe a buyout could be accelerated a bit. But regardless, my feeling still is that they should be allowed to run for a while before any money is put on the table for them.