Yes. We must donate steem power to witness so that they continue to work for steemians. Moreover there are many spammers due to which the block size is growing. This requires extra effort by witness to reduces the effect of such spammers in community. I read an article on how spammers are earning and how they are burden to everyone in steemit community. Witness do play key role in handling spammers
More the steempower with witness, they can eat them up. So keep donating to witness. This helps the community.
Fighting spam and many other kinds of abuse is something that non-witness can do as much as witnesses. There are many efforts made by various members of community to address those issues.
Short guide to help with this battle:
Thanks for the guidance Gandalf.