From the perspective of the seller is more interesting 🙂
It’s not quite SaaS, but in enterprise software, Autonomy to HP for $10.3b, firing the CEO of HP that sponsored the deal, and then promptly running Autonomy into the ground seems to be the Sale of the Decade so far:
In terms of more traditional SaaS, Yammer still likely holds the record for $$$ paid / ARR in $1b deals. And RelateIQ in Big But Sub-$1m deals. For now.