following up on what Faldage said, the one of the basic rules of english is "every sentence must have a noun and verb" - which, because this english, then gets fudged*! since "Go!" or "Stop!" (verbs only!) are valid--
the answer is in Go and Stop- the subject is implied.. you are speaking to the the person you want to go or stop, and they are implied subject.
In your example, "One of my favoite hobbies is soap operas" the part of the verb is implied! since the object (soap operas) are not tangible things, the implication is, you must have some way of accessing them.. (that is you watch them on television) since they are only available by watching, we use the gerund form of the verb, watching -- and is watching, (a verb phrase) is the verb.
with many hobbies, the gerund would just pop in..
my hobby is skating
my hobby is running
my hobby is swimming
my hobby is bikeridding
my hobby is ......ing
"implied" verbs are all to frequent when dealing with english, a language that claims to require one in every valid sentence!
One way i deal with verb/subject agreement, when i am unsure -- is to "recast" the sentence (and in another thread, someone just gave the proper rhetorical term.) by recasting, i mean move the words around and rewrite the sentence..
Of my hobbies, the favorite one is/are.. and in this form of the sentence it is much clearer that favorite one is the subject, not hobbies.! if you added watching or acting in, to the is, it would make the sentence even clearer.
an other hobby that might generate the same problem could be oil or watercolor painting
(One of my favorite hobbies is watercolors.. (the implied verb is painting but you could also use creating.)
always remember the revolutionary chant of the americans
"No taxation without representation!" (and the verb there is? Implied!-- this is what the chanters want -- but they leave off, and imply both the subject and the verb the "I Want" part!)
*fudge/d is an american slang term for breaking rules...
if one is not total truthful, or cheats, or break rules, they can be fudging-- "i fudged on my taxes, and didn't include all the cash i earned working weekends."
"i fudged a bit on test, i heard the morning class complaining about the essay question on XXX, and during lunch, i reread that chapter" or classically, " i fudged a bit on my age.. there is no reason for them to know i am over XX!"
