Polite vendor execs used to call it "coopetition"--the state of tech industry affairs whereby the fiercest of rivals could be the chummiest of partners depending on the circumstances and the market they're chasing. A more up-to-date and colloquial description of this industry dynamic might be: All bets are off. Some recent evidence:

• IBM and Sun, once bitter rivals owing mostly to IBM's early support of Linux, which undercut Sun's low-end servers, are now reportedly in talks to merge.

• Sun ended up releasing Solaris, the jewel of its high-end server business, as open source code and is now making its way into cloud computing by offering to give away its cloud infrastructure to potential competitors.

• Oracle CEO Larry Ellison, who last year was slagging off the cloud computing movement (and players such as Salesforce.com) as only so much drivel, this week was trumpeting Oracle's commitment to and investments in cloud products and infrastructure.

• Amazon Web Services has established itself as a leader in cloud computing, partly by offering branded server, database, and other IT products from the likes of Microsoft, Oracle, and IBM on its cloud platform. But as Microsoft, Oracle, and IBM power up their own cloud offerings, you can bet their relationships with Amazon will cool considerably.

• Cisco, with partners VMware, BMC, Intel, and Microsoft in tow, is now taking on IBM, Hewlett-Packard, and Dell in blade servers. At the same time, HP is digging deeper into Cisco's switching business. John Chambers, CEO of Cisco--which lists HP and IBM among only a handful of Strategic Alliance Partners--is unfazed by the complexity: "We focus on market transitions, not competitors. You've got to play the hand this market has dealt you."

What are some other recent examples of dogs and cats living together in this fast-changing, consolidating industry?