$5/mo is not a barrier for entry into anything.
Their alternative to make any dime would be to feed your text to a contextual targeting engine and serve you ads. You know how long it takes to make anything from that? No less than 100k users; for that many users, at 10 posts each user, and each post about 100bytes, they're looking at just 1GB of text a month.
A whole text mining engine, developed/integrated by 1-2 developers over 1-6 months, just to handle 1GB/mo :-( How many of those posts are read more than once? How many are shared? How many are publicly visible?
Even if you categorized the posts by a targetable "vertical", you will have about ~50 posts per vertical, and those 50 are viewed by no more than 50 people, a few times.
In other words, not fucking worth it.
For this to be sustainable by advertising they will have to make the posts public, interlinked (i.e. structured in some manner, via a social-graph maybe?) and most importantly viral content that others will seek, share and return to.
I have never seen a TODO list or a shopping list that was either viral, applicable to more than one person, or for that matter publicly shared.
So let them charge $5/mo, and let those who can afford it use the service. Developers don't need to go cheap and price themselves down to homelessness.