They may not read image maps. They may not read frames. You need to anticipate these problems, or a search engine may not index any or all your web pages. Expect that some of the search engines won't be able to index them. Consider creating static pages whenever possible, perhaps using the database to update the pages, not to generate them on the fly.
Search engines tend to choke on it.
It's worth taking the time to make your site more search engine friendly, because some simple changes may pay off with big results. Even if you don't come up in the top ten for your strategic keywords, you may find an improvement for strategic keywords you aren't anticipating. The addition of just one extra word can suddenly make a site appear more relevant, and it can be impossible to guess what that word will be. You should also consider negotiating reciprocal links with sites that do appear in the top ten lists, if you are having no luck. After all, your site may appear first when slightly different keywords are used.