Re: 90 of the Fortune 100 companies are now Lync customers
Lync client alone does not a Lync customer make.
Those customers however could be using Instant Messaging and Presence without Enterprise Voice (a common deployment first step) - but even that requires Lync server (or Office 365) and licenses. That would count as a Lync deployment, but it would only enable peer-to-peer voice chat.
Full disclosure I work for a company that deploys & supports many telephony solutions including Cisco, Avaya and Lync.