The usage of denen
I understand the conventional use of denen as a plural dative relative pronoun, but lately I've been seeing it used in different circumstances. Could someone explain what the meaning of denen in these sentences are? and why it's being used?

"was ist mit denen? denn bin einer von denen."
"dann schick denen den infovorschalg doch einfach."

Question

The usage of denen
I understand the conventional use of denen as a plural dative relative pronoun, but lately I've been seeing it used in different circumstances. Could someone explain what the meaning of denen in these sentences are? and why it's being used?

"was ist mit denen? denn bin einer von denen."
"dann schick denen den infovorschalg doch einfach."

Answer

Especially in spoken German, "der, die, das" (and all their forms, therefore also "denen") are often used as demonstrative pronouns - sometimes to lend emphasis, sometimes to make it sound a little disparaging, sometimes to avoid confusion/differentiate between "Ihnen" and "ihnen".
"Soll ich den Brief an X und Y schicken?" - "Schick' ihn lieber an A und B." - "Okay, dann schicke ich ihn denen." (here, "denen" is used to make it clear that the speaker means to send the letter to those last mentioned, i.e. A and B. IMO "ihnen" would not serve the same purpose. Also, it serves to avoid the awkward "ihn ihnen".)