I just cleaned up an older post, and a partial copy of it, that was spam (although for an LP-hosted site, so it wasn't totally removed). There were two problems with these rewrites, such as
RewriteRule ^talk_to_us_about_our_low_low_prices_and_highest_quality_workmanship_with_name_brand_materials_today_and_not_tomorrow\.html index.php?page=4 [L]
First of all, no one is ever going to type in a file name that long. The idea is to have a product name or a couple of choice keywords, and not a full sales pitch. Secondly, SEO won't help you because words separated by underscores _ are treated as one long word, and a potential customer would have to type the whole thing in exactly. You would want to separate words by hyphens - so that search engines recognize the separate words!