Right. Drake got to where he is partly due to him being on other rappers' songs, but I think a big part that people forget is that he was on TWO songs with Rihanna. Take Care and What's My Name were huge songs, I remember What's My Name being played on the radio constantly. So for a rapper to reach a bigger stage, they usually have to slightly cross over.
Now, this is where the term 'sell-out' becomes muddled, because I believe it's only selling out if the sole reason of doing it is for the sake of money, and not because you genuinely fukk with said pop artist. It also has to be something that the rapper in question would legitimately spit on, if the pop star were removed from the equation. So if Kendrick made a song with Katy Perry, he doesn't even genuinely like her music, and it's some typical Katy Perry-esque single, then that would be selling out (imo). Drake obviously genuinely fukks with Rihanna (not to mention, Rihanna being Hip-Hop affiliated..), so it works for him, and Kendrick apparently genuinely fukks with Taylor and vice versa, so it works there too.
yea the only thing that sucked was Kendricks verse.