Just from the beginning of April my site faced a problem of 50% decrease in number of visitors from Google. There is no any indicator of this occurrence except I found that many of pages indexed in Google now have no title and description in search results for my site (58000 pages are indexed in Google)...
First, I want to understand why Google remove Title & Description of many pages of my site's indexed pages?
Second, Please let me know that I'm using URL ReWriter technology for my site and increased 3 times number of pages/urls by this and it is in practice effectively from last 2 years... may it be a reason?
It happened me the same problem, April it began really bad.
In my case, I had the same metatags in all my pages of my web and I believe that it can be the reason of this inconvenience. For it, I began to reform the metas 'description' and 'keywords' so that they are descriptive of the content of each page.
The idea on that I base myself is that G doesn't keep in mind the metas for the searches (that is known by all) but they work as an approach to determine the duplicity of the content among the pages inside a web.
I will see that it happens, I prove with this, worse it is to stay of crossed arms while my webs collapses.
I am having the same problem. About 90% of the 30,000 pages listed in Google are indexed without title and description. It used to be different, but doing a search for "site:example.com -foo" returned mainly just the url.
I've seen similar for a new site. The site went live at the end of January. In late February GoogleBot visited and scanned the site pretty heavily. Many of the pages are low-content so I didn't expect many of them to show up in the index.
When I started tracking on 8-March I had 3 URL's with one fully indexed. By 14-March I was at 10 URL's with 7 fully indexed. On 23-March it dropped back to 10 URL's with 4 fully indexed. Finally, on 4-April it went to 6 URL's with only one (the home page) fully indexed.
Interestingly, something similar happened with Yahoo. Yahoo went from 27 pages indexed to one (the home page again) over the course of a week. Not a very good start. The only index with anything of consequence left is MSN with 61 pages indexed.
Someday, I hope the indexes come back to life. In the mean time I'll keep tweaking the site and adding in information.