The indie author community is getting bigger all the time, and it's important that you get some sort of edge or advantage in order to stand out (and keep selling books). So it becomes necessary to work with other indies and book bloggers who are part of the community. But be wary of exchanging favors. When you trade gifts, you may not get something of equal value in return.
You know how it works: you scratch my back, I'll scratch yours. What's in it for me? What do I get out of this deal? Nothing comes for free. There are a thousand cliches all about how you have to give in order to get, and that's kind of how it works when it comes to exchanges within the indie author community.
You can't join a forum group without bumping into a review-exchange thread, or shake a stick without seeing a dozen posts about trading blog follows fall down around you. Like my Facebook page and I'll like yours. Follow me so I can follow you back. The list goes on and on...and on. And if you actually wade through 13 forum pages and like all those blogs and Twitter accounts and Facebook pages...how many people do you think will actually return that favor?
Not very many. Exchanges are tough because you may wait a while to get your return gift, and it mightn't ever come. Review circles are hard to manage, and people who read forums disappear. Twitter accounts get suspended, and Facebook interest fades away. Exchanging favors can work up to a point, but you can't rely on help from the community to sell your books.
The thing about swapping is this: those other indie authors all want something, too. They want to sell books just like you do. So it may be a good idea to exchange a few favors to get something valuable -- a guest blog post, a spot on a prominent book tour, a great many more followers, a few book reviews. But lots of random following and review-promising isn't going to go very far, because promises easily given are also easily forgotten.
Exchanging favors becomes a waste of time if you do it all the time, and it takes away from more focused promotion you could be doing. So use your favors wisely to get something truly valuable from them, and work on individual marketing that really does succeed.