Can physical distance affect the behaviour off a webapp?

I wrote a relatively simple web application that is currently hosted on my Heroku account.

The physical server is located in the US, as am I. When I test it from here, everything seems fine. However, my friends in Asia are getting some weird behaviour, for example a timer is acting funny, and the database is sending them some things twice.

It doesn't add up.

I'm wondering if perhaps geographic distance could cause these anomalies.

Any ideas?