The decision to run my own hardware is due to the extremely high cost of storing and moving ~80TB around on the cloud, as well as running a high-memory MySQL instance. I haven't priced it recently, but the last time I looked it would have raised my costs by an order of magnitude.
I can understand that, but have you considered a pay-per-use / tiered business model?
It's clear from this thread that there are users who have thousands of bookmarks, using dozens of GB of storage, and those who use it much less and whose storage costs are negligible. Having either group pay a flat rate doesn't make sense to me, and you end up losing revenue either way.
A tiered model could allow you to offset the cloud storage costs, maybe migrate things into the cloud and ease some of the maintenance burden on yourself.
