Feedgrab has a solid cohort of regulars but a long tail of tyre-kickers who tried the product and don't often come back. I'm considering implementing a 1-year purge for these accounts. If you don't use it for a whole year, and after being given notice that this will happen, your feeds get purged. There's a cost in continuously grabbing articles for dormant accounts so I think this is a reasonable compromise for a free app, don't you? 

I'm also considering the same for free Pagecord accounts. If you sign up but don't post anything, your account will get deleted after a year.