Is there any concerns if performing Blacklists and Whitelists

The simplest filtering methods for spamassasin are the blacklist and whitelist. Blacklist entries block all email from an address or domain, and whitelist entries bypass all filtering for an address or domain. To add blackist or whitelist entries to your salocal.cf.in file, simply add lines in the following format:

blacklist_from sales@traveloforange.com
whitelist_from bill@yahoo.net
blacklist_from *@emn-mysavingsnow.net

as per in the wiki Improving Anti-spam system - Zimbra :: Wiki

Valuable suggestions are highly required..

Thanks in Advance