I've written more about this here:
http://www.slideshare.net/jdavidhill/marketo-email-reputation-management
and here:
http://www.marketingrockstarguides.com/subscription-management-tips-for-marketo-454/
As Courtney noted, you would need several pages and fields to manage this well.
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Which channels or communications can people subscribe to?
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Which audiences should see what - these pages need to be coded on to separate LP templates.
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Admin > Email > you can copy out the default text, then insert a clear or white dot or even <P></P> to remove the default from emails.