Simple answer is: it depends.
If you have soft water, and are trying to keep fish that like hard water and a high pH (like mollies and Malawi cichlids), lots of wood isnt a good idea as tannins released will lower the pH.
Obviously stuffing a tank full of wood (or any decor) is going to reduce water volume, which will decrease the dilution of toxins like ammonia, so
extreme amounts of wood are bad in those situations too too.
Lots of fish love tannins and a low pH though (like betas and rams), so in some cases it's practically impossible to put too much wood in the tank, as the chances of the pH dropping below 5 or 6 are very low.
Remember, driftwood and bogwood are different things. Bogwood tends to sink and releases lots of tannins, driftwood floats at first and generally releases less tannins.
Also, for freshwater tanks, it's advisable not to collect any wood from sea beaches
.