Although many users simply click “Save” and give no thought to which format is being used under the covers, this unthinking use of the word processor's default settings is a recipe for vendor lock-in. In fact, several vendors intentionally set their default format to be ones which will only work well with their own software, fostering dependency on that vendor's software and lessening the user's ability to take advantage of other options in the market. The more documents you save and accumulate in a vendor's proprietary format, the harder it will be for you to consider any other choices.