Just Dance 1 Scrapped Songs

I heard about this as well!
For shake i think Sam Cooke's death before the song releasing might've been the reason why it was cut.
As for the others i think it was either limitation issues such as them not having plans for how duets would work yet or something to do with copyright. Or perhaps the developers could've simply not had any choreography ideas for them at the time.
There's a lot of weird beta content in these games to be honest. Some of it is very shrouded in mystery and not many people really seem to be doing much research with it beyond finding it in the files/ads. It'd be nice to take a deeper dive and see if we can dig up more information on these songs and why they were changed,cut,or released later than intended.