Services like @smartsteem (smartsteem.com) offer vote trading . By exchanging your SBD for votes, you are not only gaining a potential profit, or tipping a user further for a good post, but increasing the SBD volume or the gridcoin tag, plus potentially making more people see the post.
You can buy upvotes for any post that is less than 4 days old.
FYI if you buy votes on a post more than 3.5 days old @grumpycat will flag you into oblivion.
Sounds like there is a story to it? :)
Haha, not me personally. I don't buy votes. However, there have been several posts related to this on Steemit's front trending page for weeks now.