If yes do not panic or think it is some kind of a spam attack to your site or a bug on the webmaster tools. It is not even your SEO or client having a secret spammy link building strategy but this is as a result of Google Caffeine working efficiently to index more and more data per website.
Due to Google caffeine going live from all Google datacenters, indexing is much faster, fresher and it collects more data for every website.
So, atlast you get a clear picture of how widespread your website is as the link:domainname.com parameter in Google never gave the right information of no of websites linking to your site.
Caffeine has indeed made the website data lively !
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