Netapp needs something new, in the all Flash array area. Their FAS line of products are very good (IMHO) but for capacity needs. Nor performance needs. Their E-series line are good products too, with much better performance, but whithout any advanced feature. And they still can't compete with Full Flash actors.
It's why they have to push out a new solution, either custom made or thanks to shopping cart !
This is what is behind the confidential "Mars Project". And the timeline is probably arround Mars 2013 ... So this is why I think that Netapp might be interested in buying Violin.
Moreover, everybody know that Netapp like "All in one " Box, with SAN (FC, ISCSI, ...) and NAS (CIFS, NFS) features. And in november 2012, Netapp secretly bought CacheIQ company , which similar feature as Gridiron, but in the NAS area...
So if Netapp Buy Violin, they will have all the necessary technologies to build a very interesting full flash solution: Violin for the Array, Gridiron and CacheIQ for the cache (so they could stop using Fusion-IO technology), and their own technologies for everything else (management, dedup/compression, ...).
Of course, this is all pure speculation from me. But I think It makes sense, in a technical and business point of view.