With the new groups system, the higher, honor groups, require people to keep getting rep in order to stay in them. Specifically:
Distinguished Contributor requires 10 new rep in the last 2 years to maintain.
Top Contributor) requires 10 new rep in the last year to maintain.

In the past, once someone got VIP (now called "Distinguished Contributor"), you no longer needed to rep them, because they'd keep that status anyway. This is no longer true!
Now, DCs and TCs need your support to maintain their status.

So, if someone posts something great, please give them rep.
Even if they're a Distinguished, or Top, Contributor.
You should still give them credit.

You can give rep using this button:

It appears at the bottom of each post, for everyone who has attained the level of contributor and higher.
Remember to follow the rules when giving rep. More details can be read here, but the system essentially boils down to: "Give positive rep only for posts which are, objectively, a substantial contribution to ADISC. Do not give positive rep simply because you agree with someone's opinion."