I think that's called spamming, unless someone brings it up. Having said that, I don't know if anyone has ever mentioned it on bigblueball or whatever, they had an AIM forum. It has been mentioned, at length, on MessengerGeek.
TINYTEXT 256 bytes
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MEDIUMTEXT 16,777,215 bytes ~16MB
LONGTEXT 4,294,967,295 bytes ~4GB Those who follow the river, can fall in.