Exchange Concentration
Most trading, price discovery, and often custody for an asset sit at one or two venues, so a venue's problem immediately becomes the asset's problem.
How it happens
Assets are typically listed on a long tail of venues but traded meaningfully on very few, and the venue with the deepest book sets the reference price that indexes, oracles, and other venues follow. That single point carries several exposures at once: a withdrawal halt traps supply, an outage removes price discovery, a delisting removes the main fiat gateway, and a regional access restriction removes an entire user base. Because the same venue often custodies the asset for many of its holders, market structure risk and counterparty risk arrive together rather than separately. Concentration also makes manipulation cheaper, since moving one book is enough to move the reference price everywhere.
What you can actually observe
Look at volume share by venue after filtering, at which venues feed the relevant index or oracle, and at whether the asset trades meaningfully in more than one regulatory jurisdiction. On-chain balances at exchange-labeled addresses show how much supply is custodied where, though labeling is heuristic and should be treated as approximate. Historical outages, withdrawal pauses, and maintenance windows at the dominant venue are documented in its own announcements.
Precedent
Mt. Gox handled the majority of bitcoin trading before it failed in 2014, and its collapse disrupted price discovery as well as customer balances.
What makes it more or less material
Check the share of filtered volume at the top venue, how many jurisdictions offer access, whether oracles and indexes depend on that same venue, and how much supply sits in its custody.