The contents of a webpage are crawled by a search engine and the most common words and phrases are collated and identified as the keywords for the page. LSI looks for synonyms related to the title of your page. For example, if the title of your page was "Classic cars", the search engine would expect to find words relating to that subject in the content of the page as well, i.e. "collectors". "automobile", "Bentley", "Austin" and "car auctions".
LSI will not affect a squeeze page that has no intention of achieving a search engine rank anyway, due to its minimalistic content. But for site owners or bloggers hoping to get on the search engines good side, pay attention to LSI.
Latent Semantic Indexing is a good thing. It keeps content relevant and rich the benefits not only visitors, but website owners that produce quality material.