Open Access is a fast growing business model in the world of academic publishing and this is a gratifying development. Just as with any other successful product on the market it has attracted the attention of all kinds of people who want to get a piece of the action. Some publishers are sincere in their intentions to make a success of Open Access and have sufficient integrity to do so in an ethical and responsible way, but there is a growing number of obscure ‘publishers’ whose business operations are less than transparent. These are mainly out to make a quick profit. Known by some as ‘Predatory’ Scholarly Open Access publishers, they hunt ruthlessly for their prey.
These publishers often make use of aggressive acquisition methods such as spamming. They appeal to human vanity (vanity presses) because they see value in just about every paper or monograph and they publish the work for a relatively modest fee from the author. You may be tempted to take up their offer, but as a researcher (maybe at the start of your career) you should be aware that little or no peer review is organised for such publications, no indexing takes place in important databases, and they will not produce any citations to speak of. Many of these publishers are short-lived, which means their publications have a limited degree of permanence and will eventually just disappear.
Lists of such publishers are available, which are definitely worth consulting.