Let's go back in time 20-25 years. I was a wannabe game programmer, and every few months I'd get a stick up my ass to write a Doom clone, RTS, or whatever game I was playing at the time. I'd recruit a buddy or two from a chat room or messageboard. Even though whatever game was out there (Quake II, AoE) was amazing and something we'd never come close to, we'd start methodically planning out the game, star writing an engine, have some test art created...you couldn't stop us. At least not at the start. Eventually we'd get distracted and go our seperate ways, but we still worked on the project like it was the most important thing in our lives for 2-3 months.
Back to today. I wanted to make a chess website, just something simple where you could login and play a game with other users. Mostly so my dad and I could play without being in the same room. I wrote a simple web-based chess engine, got about 75% of the way to what I would consider a 'completed' project. Then I went to chess.com.
Now, I wasn't planning on making something even close to that. No chat rooms, blogs, rankings...but seeing all the features on the site just sucked every last drop of motiviation I had. It didn't help that my current site was basically playable and didn't need much more work. But from that point one, every time I opened my project it just felt so futile.
I know that products evolve over time, and whatever Chess.com looked like in it's first revision probably wasn't anything special. But it's like I knew that I would never even want to take it to that level, so I just lost every drop of motiviation I had at that point.