Such a drive can be exploited if you are at least a little in the subject, control its condition, copy the data to another medium regularly. On top of that, it can't be a complete s*** like Seagate DM. If the model is highly failing, the number of reallocated sectors is more than single digits in RAW, even knowledgeable people should not take risks. To complete laymen and average users, I actually recommend replacing the drive when the drive begins to physically degrade.
My record in this regard is using a defective Samsung 160GB for at least 6 years. Of the 145GB of data on it, I managed to recover some 110GB. I completely ignored its condition at the time, and that's how it ended up (hundreds or maybe thousands of bad sectors...).