Mike's nice post on endosymbiosis reminded me of a common situation found in engineering/manufacturing firms. It's a common strategy for these companies to position themselves for quick response when unexpected opportunities arise. Those opportunities might come from new technology that could be incorporated quickly into existing products or even open up new product lines. Getting to market first is key. It could also come from customers wanting some novel design in a hurry.
In either case what these firms do is prepare for unexpected opportunities. How do they do that? They create modular components with standardized and flexible interfaces that can be integrated together easily in novel ways. They maintain an inventory of raw materials and components so when an opportunity comes around, they are ready. The challenging part is deciding what to keep in inventory and how much. Being too broadly ready and you have problems with inventory turnover and cash flow. Be too unprepared and you miss the opportunity. This takes intelligence and planning, but it often pays off.
The picture of the aerobic eubacterium being incorporated into a cell, struck me as a good illustration of a chance to be opportunistic. The cell could add new functionality quickly, if it is ready. Now I'm no biologist, but I've seen it said that there is too much "junk" in the cell or DNA to indicate design. To this engineer this "junk" reminds me of the inventory of parts companies keep on hand, just in case. To the untrained eye these parts indicate poor management until the day their engineers scramble out to the bins, punch out a novel design, whip up a finished product, and deliver to an anxious customer on time. Obviously the cell can't afford too much inventory or it becomes burdensome. It would take some intelligent planning. However, with the right mix of quantity and type imagine how quickly the cell could take advantage of symbiotic opportunities that might come its way.