Is your goal to essentially become a conglomerate of niche e-commerce firms or do you eventually intend to resell the companies you acquire to others?
Equity in big, fat growing company...
Help from shared pool of resources/experts taking a company from $5-20MM (easier) in sales to $100-300MM+ (harder) in sales much, much faster...
Help widening margins on high revenue...
Probably some sweet incentives if they do... Etc...
It makes sense. This isn't particularly innovating, but I have a feeling everyone here will be cleaning house soon enough.