We've all read about how eCommerce is bigger than it looks. There are needs other than actual purchasing that eCommerce fills. Amazon, it seems, has overtaken Google in the US as the startingpoint of product-search. In order to make a purchasing decision, you need information, and an eCommerce site is (or should be, it is believed), in the business of providing the same. Therefore, what you can also do is also use eCommerce only for the purpose of decision-making, deciding what to buy, maybe even where to buy - but not actually buying.
What also happens is the reverse - people don't know what an Xperia J looks like, weigh or feel like, so they go to a mall, check it out, come back and purchase online where prices are better for the same standard product. This is split by consultants (naturally) into (guess-what) a 2X2, with segments called Research-Online-Buy-Offline, Research-Offline-Buy-Online, and of-course the other two blocks of people who complete the buying process Online or Offline. The transaction will be called Online or Offline basis where it is *consummated*. So this is the first thought I'd like you to hold on to.
The third thought is a simple question - is Cash-on-Delivery eCommerce? The "transaction" i.e. the exchange of goods for consideration really happens after the goods are delivered to the shipping address, acknowledged, checked and then paid for. The entire decision-making process and the commitment to buy has happened online, but the transaction is really offline.
Now the second thought is just an extension of the same logic to say there are people who extensively use the mobile phone to research, but then open their PCs / laptops next morning to transact - maybe because screens are larger, or keyboards are better, or connectivity is better, or just due to plain habits. The use case for the reverse is thinner but still non-zero. You could have used your laptop to make a decision (where you can actually compare four products'-specs side by side), and then used your mobile to monitor prices and then when you saw the price drop to the level you wanted - maybe you were on your way home then - you just clicked on 'Buy' on the mobile.
Now putting it all together, if you read this at one go, it will appear that Mobile Commerce is bigger than it is. If CoD is eCommerce (and rightfully so) then mobile-initiated transactions are m-commerce. That can help change perspectives of a lot of organizations in countries like India where we keep thinking m-commerce has not happened yet just because there aren't enough transactions culminated on the mobile.