They spent 362 million $ on Spring Source (WTF!) and a 100 million $ on ZImbra (double WTF!). That's enough to buy a 100 early stage startups (and a chance of getting something really innovative). As it is it sounds like a typical MB droid play.
That said, I think the above argument works if you're looking at Zimbra purely as an acquisition of technology. My view, as might be gathered, is that this - like a lot of enterprise acquisitions - is as much or more about the business that Zimbra was doing. Where business reads as: the account inroads they've made in small hosts and service providers everywhere; the kind of accounts that are crucial to VMware's future.
Whether it justifies the valuation is a question of revenues, which we don't have a good sense of, but if this helps advance VMware's larger ambitions it's certainly worth a significant multiple of an early stage startup.
SpringSource (platform) and Zimbra are in the enterprise world. Also keep in mind that both SS and Zimbra have enterprise customers.
Startups these days aren't producing CRM, ERP, HRM, and CMS... and most startups aren't platform providers.