Let's this over a little more. Looking at what Electrolux did, it would seem that the logic behind buying another company is to get one of two things; market share, (Jonsered, Poulan), or technology, (Red Max).
Makita would get neither with Efco which has laughable market share and is less technically advanced than Dolmar. When Makita bought Dolmar, their desire here in the US was to use Dolmar, (and Robin), technology to build the Makita brand into a serious player in hand held OPE. There were Makita factory reps and dealers bought direct from Makita, not through distributors. For several reasons, it never worked out and Makita scaled back their efforts in OPE to concentrate on what they do best, which is the electric tool business.
I'm not as clear on the Echo/Shindaiwa deal, but I believe Echo was interested in Shinny's backpack blowers and such. But the result in this case is that the Shindaiwa line has become sort of emaciated in the process. I believe they've gotten out of saws altogether and the rest of the line has also been paired down to the point that it really isn't a complete line anymore. Their marketing strategy seems to be to convert the Shindaiwa dealer base into Echo dealers and my prediction is that the Shindaiwa brand will be starved for product and fade away.