Segmenting your database is always important to achieve better results in your campaigns. But sometimes it's even more important due to technology issues.
Maybe you already know it, but recently GMail - the webmail from Google and the one a good share of your subscribers is probably using- has incorporated a new feature to automatically translate emails on the fly. You must add it explicitly to your GMail account through the "Labs" tab in "Settings":

Once this useful feature is finally incorporated to the product by default you'll need to be very careful with the layout issues that will arise.
Expressions/sentences in different languages are normally very different in length, so if your design or layout depends heavily on text you must be careful. If your recipients are translating your mail automatically your design could be easily scrambled.
Take for example this simple e-mail in English:

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It contains a headline and some text. The headline uses a quite big text that obviously is intended to fit in a single line.
Let's see what happens when I press the translate link and got my email translated to Spanish:

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The headline now uses two lines, and the email is not so beautiful.
This could get much worse on longer phrases and on emails that rely excessively on the size of text fit between images. So take it into account.
If you segment your database well and send contents in the right language to the right people, then -apart from probably getting a much successfully campaign in any conditions- this effect will be minimized.
By the way, the GMail translation plug-in doesn't translate links at this moment. I've reported it through the feedback option and hope that it gets fixed soon :-)