It is also important to realize both SparkFun and Adafruit target the hobbyist market, not the professional market (except for proof-of-concept and idea exploration aspects for professional developers, I guess).
While a big company like TI can reach a lot of professionals at a conference or trade show, and raise developer interest there, they almost completely miss the hobbyist market. As these smaller companies have shown, there is a valid business niche in targeting hobbyists. Exactly
how that is done, I do not know, but I do recognize a few key aspects looking at them.
My earlier point was just an observation that it seems like me that using that hobbyist niche as a way to establish a presence in the mind of those that will eventually become EEs and gadget designers ougth to be worth the financial risk, because as Microsoft has shown in the software world, just getting the mindshare early is sufficient to grab most of the market. Even when your product is not superior technically, and you acquire new product families through business acquisition, not in-house development. As SparkFun, Adafruit, Olimex, Watterott, and others have shown, this market niche in itself is profitable; it is just completely different to how larger companies like Texas Instruments and Analog Devices are used to operating.
I bet (but could be wrong) that the FOSS/OSHW approach is a big part of successfully operating in that hobbyist niche; that it is part and parcel of building a successful "brand" in the hobbyist market. Because of how different the operations are in the professional business world, I believe successful application of FOSS/OSHW there is necessarily different, probably "less pure" because of practical reasons.
However, what I keep harping about here, is that that does not mean that the big business approach is the only one that works. There are different business niches, and I believe PJRC and others have shown that mixing proprietary and open approaches (specifically, keeping all interfaces open and documented, but some inner details proprietary) has the widest variety of business niches it can be applied in. It is pretty important to notice that the Linux kernel itself has a very similar practical approach: the developers don't demand the internal details of the devices, or sources to the firmware binaries that auxiliary processors or microcontrollers run on various devices; it is the interfaces that are the key, and that all code run by the main processor is open source so that developers can examine, understand, and fix any issues. Also, not many users realize how stable the userspace-facing binary ABI of the Linux kernel is. (Except for idiotic subsystems like Alsa. But that's a different story.)
It is important to look at the bigger picture, future opportunities, existing successful businesses, and so on; and that making sweeping claims like "a business cannot survive on OSHW/FOSS" are nonsensical, similar to claiming that everybody must speak English, because <reasons>.
As to those who believe the largest companies are the most important, I'd like to point out
Mittelstand in Germany, the strongest EU economy: SMEs account for 35% of total business turnover, but about half of the total added value.