Its pretty well established that “email AT domain DOT com” offers only marginal protection from spammers getting your email address, but sometimes, it makes it even easier. Look at this google query for “at gmail dot com” restricted to LinkedIn.com
From a search like this I can harvest thousands of reliable emails off linkedin.com, or the general internet, using only the search engine context. In fact, I did, here’s 500 gmail addresses from LinkedIn with the last few letters removed.
Search engines don’t index special characters, so an email of the form “email@example.com” is protected from this sort of discovery. The basic trouble is “email AT domain DOT com” is completely indexed by search engines, and its unique enough that whenever you see “at domain dot com”, you know its part of an email address.
If you really want to evade an email harvester, put up an image of your address, use some css/js obfuscation techniques, or encode your email in a simple statement like ‘my last name at gmail.com’
Personally, I already get enough spam, and gmail provides excellent enough spam filters, that I don’t mind spreading my real email address around anyway. Go ahead, send me a note at firstname.lastname@example.org if you wish!