Is there any electrical hazard when removing a fluorescent tube?

Answer 1

The electrical connections for a fluorescent tube are quite small and also inside the lamp holder at either end of the bulb (2 on each end).
Since you won't be able to put your finger into these connections regardless of whether the lamp is in or not, there is no real electrical hazard when removing a fluorescent lamp while it is turned on. However it should be noted that this is only under normal operating conditions and if a fault is present there could be a chance of a hazard from any metal parts of the light fitting (not the tube).

If the light fitting is turned off, there will be no voltage in the fitting and hence no electrical hazard anywhere on the fitting (again not accounting for faults). This is how I would recommend changing a tube (this is not always possible where the fitting is the only source of light).

It should be noted that fluorescent tubes can heat up during operation and that dust may have settled on top the lamp, so appropriate safety equipment is recommended (gloves and goggles). You will also generally be working at height.
Lastly fluorescent tubes are glass so take appropriate care when handling.

If in doubt please contact an electrician.