IBM is a good example. In the past, Big Blue played nicely with the BI vendors whose products needed IBM's hardware, databases, and software. IBM's acquisition of Cognos turned their previous buddies into enemies.
Mega-vendor SAP acquired their way into the BI space with the Business Objects purchase and became IBM competitors.
But Business Objects had been a long-time friend with IBM Global Services who loved doing large DB2 data warehouse projects. Rather than continue with that, SAP has acquired their own relational database, Sybase.
If everybody is now your competitor, who is there to work with?
Boris adds a word of advice to the remaining small BI vendors:
"Offer your own full BI stack or position yourself for an acquisition. No other long-term options in my mind."