The main problem with micro-transactions is "represented value" - if something doesn't cost very much then the perceived value of the item is very low so it ends up looking like you're charging for something that isn't really worth the cost. For the majority of people $10/month for 100 articles represents better value than $.10 per article even though they're actually the same.
So, another way of looking at it is the app store/app upgrades way. You pay using smaller increments, but have a view of the goods that you are buying. So instead of a future commitment, its more about paying for what you want now.
If its seamless, then micro transactions work. It also implies you are distracted enough not to do a future projection of the longer term aggregate costs incurred :).
