The Drophonl is easily categorised:
They leave crafty markers (formerly known as a "comment,") in early posts- hoping to catch the blogger unawares.
They have an encyclopedic knowledge of random, useless information and demonstrate it whilst in mixed company or dining out. (J A S is known for his random snippets. Need to entertain the unknown guest of a guest? Want to get rid of the party bore? You know who to search out.)
They have weak posture- real slumpy y'all.
They wear those courtesy hotel slippers whilst in their own home. Though we all know we paid through the nose for those tissue thin, one size fits no-one mules.
Do watch out for the Drophonl in your community and make sure you report them to your local busy body- unless they are making themselves useful by boring the pants off the party bore.