There is a single post at WebmasterWorld where a senior member is complaining that Bing has reduced the number of pages they have indexed of his site.
He said he had about 500,000 URLs URLs indexed and now he only has about 350,000 URLs indexed at Bing. This occurred around May 5th.
So I checked several of my sites at Bing Webmaster Tools and didn't notice a change in the index rate at all for any of my sites. In fact, here is a screen shot of the index rate for this site, as you can see, there was a little increase one day on May 3rd or so.

But when I looked at my traffic, impressions and clicks, there was a huge change - for the better - on May 7th or 8th:

I also noticed fluctuations in the crawl rate chart, but that seems normal - to be all over the place:

Have you noticed any significant changes at Bing recently?
I am thinking maybe the increase I am seeing is related to the Bing social integration or maybe not?
The last possible Bing update was in late March 2012 according to my records.
Forum discussion at WebmasterWorld.

Comments:
William Vicary
05/15/2012 01:26 pm
You mentioned your site had more traffic POST penguin - does the increased Bing traffic correlate to the pages with more traffic from penguin?
Barry Schwartz
05/15/2012 01:39 pm
I specifically isolated Google traffic and it was/is up about 50%. Bing also is up significantly but more recently, not as of April 24th. As you can see from the chart.
Enrique Gonzalez
05/15/2012 03:49 pm
What I noticed is that when checking site:domainname.com it dropped substantially like to 30% of the previous numbers. BUT when checking the BWT indexed pages continue increasing, traffic shows a peak on May 8-9. Any clue on this?
David Eaves
05/15/2012 07:46 pm
Yes just checked and my site has started ranking much better, thanks for the heads up.
kevinanchi
05/16/2012 04:49 pm
This fluctuations is normal for bing and i am noticing it for months for my site, its like roller coaster always up and down, wonder how this impacts on the traffic..... i have not noticed any change in the traffic though
William Vicary
05/17/2012 12:27 pm
Sorry I meant, if Bing are still using the G results (or users searching on G via IE) then it is likely after a short period that you would see an increase in traffic from Bing for the pages that experienced a lift in traffic also?
Bryan Tuck
09/05/2012 01:39 pm
I noticed that where Google indexed 300+ pages for a site Bing only indexed 19. That is a huge difference.