Just dropping your affiliate link on Twitter won't work: you need to select a better, higher-quality approach.
Write good content, integrate affiliate links in it and promote your content on Twitter. Thus you won't sacrifice on quality of your Tweets and will drive good traffic to your affiliate site.
The so-called "in-direct" promotion will prevent you from losing friends and help build relevant readership (which means conversions and earnings):
#Send links as a natural part of conversation (in reply maybe);
#Tweet personal messages, not canned ones;
#Don't be all about yourself (participate and contribute!)