Microsoft announced today that Bing is just now supporting query history in its Autosuggest feature. In other words, if you have your search history enabled, Bing will incorporate past queries you've made into the suggestions.
"You are in full control of your query history," the Bing Team stresses. "We know your privacy is very important to you. You can turn History on or off at any time or selectively remove any portion of your search history using the Manage History option. You will see both of these choices every time you use Autosuggest."
"Many search tasks span multiple search sessions even days or weeks," Bing says. "In fact, 44% of non-navigational search sessions last longer than 1 week! Perhaps you need to research the purchase of a new automobile. You might use Bing to find a retail location and to further research online – over many days – to make the best decisions on your big ticket purchase. With history support in Autosuggest, you can restart a previous search session by typing a few characters to see your previous queries and start researching right where you left off. We know from our testing that this makes you more effective at your longer search tasks."
The suggestions that are based on your search history are listed in purple, to stand out from the other blue suggestions.