By the way, Canon imaging sales did okay in 2012 (business in the black), like Ricoh (in the black too). Nikon did less well than expected, and was a little in the red in terms of sales, if I recall correctly. Other imaging corporations (or imaging divisions of a corporation) were either just okay or a little in the red. Some were not doing very good (Olympus), but none looked in danger or anything...
In theory, and under the same management, smaller companies usually can turn around faster to adapt to the market's changes than bigger ones.
But in practice, management is key to how a company can survive in an ever-changing market. The best example is Kodak... It used to be the biggest photo company in the world. Several times bigger than Nikon. And when digital cameras first were introduced on the market, Kodak was manufacturing most of them. But they ended up filing for bankruptcy anyways. The big size of the company didn't helped when it was time to turn around, but it probably went down because of some bad decisions made by management (like introducing 7 new APS film cameras the year Canon and Nikon stopped introducing new 35mm film cameras to focus on point & shoot digicams).
Still, a smaller company usually has fewer employees, which results in lower operational expenses, and has a higher cashflow-to-borrowed money ratio in its operational budget which means it's usually less affected by interest rates or (not too big) financial losses. That can make a company more "agile" in the business world, for it doesn't need to borrow more money to put capital into new technologies when the market is changing and its operational costs are low. A bigger company can end up more in debt when sales don't meet expectations, which can reduce its ability to change its orientation as swiftly as a smaller company.
But then, if the company is specialized (example: a super thin electronics copper wire products manufacturer) and that its specialization becomes obsolete because of a new technology, it can disappear in no time, no matter how agile its small size makes it into the economical world and how good its management is. They often lack the financial power a bigger company could have to change its business into something else before it's too late.
Example: Canon manufactures lenses, still and digital cameras, but also broadcast lens components, printers, copiers, chipset manufacturing machines, scientific optical imaging stuff, etc. So they could adapt better to a drop in camera and lens demand, thanks to copiers, chipset manufacturing machines, etc. They can develop business into different markets as well, for they have a wider range of activities that makes them a solid name in other things than just cameras.
Nikon's business, on the other end, is mostly concentrated in still cameras and lenses, with a fair part of sports optics, microscopes, optics and scientific optical imaging stuff completing their portfolio. If the camera market was to suffer a lot from a big change, Nikon could be much more affected than Canon in the same circumstances. This is what happened in 2012 and 2013, and it will probably go the same way in the next years to come, before the market stabilizes a bit (less entry-level point & shoot to the expense of mobile devices, a more frequent DSLR update to make up for the decreasing market of first-time DSLR buyers, etc.)
All-in-all, I'd say a smaller size can be an advantage in business, but it depends a lot on the business type you're in and, mostly, how good your management is.
But I'm no expert on this subject, so consider all of the above as being just my two cents.