is it okay promoting affiliate programs via tweets?

Hi guys,

my twitter accounts (Over 15000 followers) are giving me and some of my client's sites good traffic. Am scoring minimum of two dollars from automatic revtwt tweets too.

My doubt: as am getting good number of hits from my tweets I have a plan to promote my affiliate programs with twitter tweets.

I would like to know,

i) will there be any problem with twitter, as am gonna promote an affiliate program? I don't think that there will be any difference in the tweet than a normal tweet with a url.

ii)will it cause me any problem with the company who provides affiliate programs? is it a violation of rules?

Please give good advices...