There are many things that cause data loss in Salesforce. They are :
Human error :
* When editing an object definition (incorrectly changing a picklist), importing data (overwriting good data with bad), or merging households are the common situations where human error may occur.
* For example, when you import data, it becomes important to match up fields. Situations like moving to percent, number, and money from other data types or changing text area to URL, email, phone or text, etc. will lead to incorrect match in fields. If you are updating a large number of records and match up incorrect fields, your records will be invalid.
Accidental deletion of Salesforce data :
* A record (or multiple records) might be accidentally deleted by users or employees. Deleting records could be because of miscommunication, forgetting to remove a contact from being deleted, and many other reasons. So proper training and having a trusted backup/recovery solution are much important.
Purposeful deletion of Salesforce data :
* Disgruntled employees like the person who has recently got a very bad performance review and thinks their job is at stake or who is jealous of other employees might try to delete the data. A few clicks on the delete button may lead to the deletion of multiple records from Salesforce.
* If they empty their recycle bin, that data recovery will be difficult using the Weekly Export. It can cause numerous damages if these records are not backed up properly.
Data sync errors :
* If you have more than one admin or use Outlook for Salesforce, you might experience a data sync error at some point.
* For example, one admin is trying to refresh a sandbox while another admin is working from home and trying to edit an object type in that same sandbox. When this happens, the admin who was editing the object can lose his work in progress.
* Contacts in Outlook can over-write good Salesforce data when using Outlook for Salesforce, introducing errors through inappropriate sync.
