Twitter is promoting accounts in people's "following" lists, regardless of whether or not the person actually follows that account. This is starting to draw some attention and criticism, as some find it to be misleading.
MasterCard appears to be the account everybody (including myself) is seeing.
As Marketing Land points out, MasterCard is even listed in Visa's "Following" section.
It doesn't really come as much of a surprise that Twitter would place these accounts here. It's one of the prime places on Twitter where users can discover new accounts to follow. If you're looking at someone's account who you are interested in, there's a good chance they're following some interesting accounts too.
The problem, as some see it, is that these ads make it look like users are following accounts that they're not. This could be problematic in cases where the person specifically does not like the brand.
The ads are labeled as promoted, so it's not totally deceptive, but that's also easy to miss if your'e quickly glancing through accounts.
Update: Various reports that covered this topic are now including updates after getting comment from Twitter saying that these ads have been showing since 2013, without any changes, though for some reason, more people have been noticing them after William Shatner tweeted about them. Either way, if they've been around that long without people noticing, that would seem to only illustrate the misleading point even further.
Image via Twitter