You can combine the new attributes. For example, rel="nofollow sponsored ugc" is valid.
Paid links must use the nofollow or sponsored attributes alone or in combination. Using "ugc" directly on a paid link may result in a penalty.
Publishers don’t have to do anything. Google neither encourages change nor penalizes inaction.
Publishers who use nofollow to control crawling may want to rethink their strategy.
Because Google wants to take back the link graph.
Google introduced the nofollow attribute in 2005 as a way to deal with comment portugal mobile database spam and illegitimate links in user-generated content UGC. Linking to spammy or low-quality sites can hurt you, and nofollow gives publishers a way to protect themselves.
Google also requires nofollow for paid or sponsored links. If you are caught accepting anything of value in exchange for a link without the nofollow attribute, Google may penalize you.
Large sites like Forbes and Wikipedia have applied nofollow across their entire site due to fear of being penalized or not being able to properly police UGC.