This isn't exactly about a feature. Features are the verbs of a web/mobile product. Objects are the nouns. And one thing I always like to think about is what is the most fundamental object of all in your service. I like to call this the "atomic unit."
Here are some examples:
In Twitter, the atomic unit is the tweet
In SoundCloud, the atomic unit is the sound
In Turntable, the atomic unit is the room
In Tumblr, the atomic unit is the post
In Codecademy, the atomic unit is the lesson
In Wattpad, the atomic unit is the story
In Etsy, the atomic unit is the item (although one could argue it is the seller)
In Kickstarter, the atomic unit is the project
In Disqus, the atomic unit is the comment (although one could argue that it is the thread)
In Instagram, the atomic unit is the photo
In Kik, the atomic unit is the private message
In LinkedIn, the atomic unit is the resume
In Foursquare, the atomic unit is the checkin (although they may have just moved it to the venue)
In Gmail the atomic unit is the email, in Gcal the atomic unit is the appointment
In Brewster, the atomic unit is the relationship
In Dropbox, the atomic unit is the file
In Google Docs, the atomic unit was the document, in Google Drive, they would like to it to be both documents and files. And that creates some cognitive dissonance.
I could go on and on, and I apologize to all the USV companies I left off this list. I am not picking favorites. I am just doing stream of consciousness examples.
When you think about an MVP, it's really important to identify the atomic unit and make sure you focus the product crisply and cleanly on that object. If you think you have three or four atomic units, you are going to end up with a clunky and bloated experience and that is what you want to avoid at all costs with your MVP (particularly if you are mobile first).
Can you identify the atomic unit of your product or service? If you can't, then you might want to sit down and think about why you can't and what you might be able to do to address that.