1. If you are sharing computers to create your Fitbit account and do the Fitbit to Walkingspree connection, it is VERY important that you logout of Fitbit when you are done.
If you have accidentally "allowed" someone else's account, to correct this, log into Walkingspree, click on My Apps. Uninstall the Fitbit app and reinstall the Fitbit app with your Fitbit credentials. Double check that it shows your account before you click allow.
2. If you want to share dongles/computers, it can take up to 15 minutes for the data to sync to Fitbit. So you may need to be within range of the dongle for up to 15 minutes for the data to sync.