Some grammatical errors become so common, they are integrated into language. Words like forever and alot are prime examples. But some mistakes are still wrong, no matter how often we hear them. I seen is the one I hate the most.
On the Grammar See-Saw
I don't care how you phrase it or use it, I seen is incorrect one hundred percent of the time.
The verb to see is irregular. It has several tenses, like any other verb. The present tense is simply see, as in I see you reading that blog post. The past tense of see is saw, i.e. I saw another blogger writing about that last week.
And then there's seen. It is the past participle of see. This means it's only used with another word, like have. For instance, I have seen better blogs. The word seen only works with other verbs, but it doesn't get along with nouns. To use it properly, it's got to have one of its friends. Words like have and has make seen a possibility. Without them, you've just got bad grammar.