De-anonymization would take monitoring over a period of time, but it could definitely work. Take this scenario for example: a person of interest is in the area of New York on Jan 1. On Jan 4 they travel to the UK. On Jan 7 they travel to Germany. On Jan 21 they travel back to the US.
The list of suspects would be fairly small when US officials cross-check individuals that travelled US-UK on Jan 4 and Germany-US on Jan 21.
The list of suspects would be fairly small when US officials cross-check individuals that travelled US-UK on Jan 4 and Germany-US on Jan 21.