@ RobynYoBank:
Not trying to get at you like the others (give him/her(?) a break, whatever

), but judging after my impression of Ke$ha having seen her interviews, shows, private videos etc. etc. and even only judging by their music, I think there ARE big differences between them as artists. I don't think that Ke$ha, as an artist, is taking a lot of influence from Lady Gaga in any way. I just don't think she does. It might rather be her record label who saw that Lady Gaga's concept (LP + EP + Remix album) was very successful, so they thought: why not try the same, it could work. So they might have talked to Ke$ha about it, she liked the idea as well and so they did it.
The idea to incorporate 70's rock'n'roll into the next album certainly came from her though imo and seems very genuine to me. She has always said that she loves this kind of music, listens to Iggy Pop, Led Zeppelin and Sabbath all the time etc. So that again must not have anything to do with Gaga's similar approach for BTW. They are to some extent just inspired by the same artists and musical genres I guess.
That's how I see the whole thing. I think Ke$ha draws the majority of her artistic influence from music and artists who were big in the 70's and 80's, and that the obvious similarites are more of an incident. But of course I can see why people would point out those similarities.