The only harm I can see from it is wasting all those trees 
and my wife getting mad because she can tell what denial letters look like in the mail now 
(She is a firm believer I dont need to apply for so much crap, so often but I like to know where I stand)
I have not read any stories of anyone being told they are requesting too often or having an account closed or penalized for too many requests.
I request from comenity about twice a month. (they seem to give me 1 cli via online a month, i just have to narrow down that 1 month date and havent yet so I apply mid and end of month)
My actual cards (Visa/MC/Discover) I request multiple times a month, probably about once a week. (More often when I see mass people saying they are getting CLIs on specific cards here in the forums) I still get auto CLIs at times youd expect from them so they must not mind.
(Overstock I was told auto gives 200 via online CLI when you get your account and it was true for me)
Ive talked to reps on the phone before and have been told by more than 1, you can apply every day for an increase on your account if you wish it wont make any difference to them, but if you were denied one day you probably wont be approved the next. Some of them have told me to apply every 2 weeks or so if I am wanting an increase and have just been denied.
I wouldnt worry about it, I dont think it harms anything.
