[levosmetalo]

Shut down the free service and no one will get hooked to your product, and choose a another free service to start with, and maybe even pay for it later.

Providing both free and payed tier is the way to go, especially in the commodity market segment like RSS readers, unless you are in a niche without too much competition.

[btipling]

I disagree. RSS readers have a significant long tail expense per user. I worked at Bloglines. Pretty much every one of those free users have extra little RSS feeds that nobody else subscribes to that you have to crawl, handle invalid rss/xml for, update and keep unread status on. At scale, that is the most expensive part of operating an RSS reader, and it's not worth it.

[levosmetalo]

I agree with your point that keeping RSS user is not free. But, from the users perspective, RSS readers are a commodity. You can't sell them subscription unless you provide them a free ride to actually check and hook up to your service. The only reason that OP is successful is having a business model working is that he already has a large userbase which was acquired largely because it was free.