Snowball sampling is a method for identifying network entities in social network analysis that involves asking network members who they are connected with and adding them to a continually growing list. This is in contrast to a bounded list method where network members are asked to select from a list of pre-determined members. 

The benefit of snowball sampling is a more comprehensive list of network members and a larger and more complete network map at the end of the process. However, there are multiple challenges with snowball sampling. Most significantly, different network members often refer to the same partner using different names, spelling, and acronyms, requiring a significant degree of data cleaning before you can map your results. Additionally, snowball sampling can introduce more 'noise' in your data by expanding the scope of the project and make it more difficult to spot key insights or answers to your specific questions.