The growth was pretty steady, but I was always extracting the maximum from the hardware I had to save money, so for a long time I had intermittent issues. I also had my own server colo'd for a while, which I do not recommend for a one man shop. It nearly broke me a few times having a server go down and spending all day trying to fix it. I had a sever go down hard 2 days before I got married, but I had to let it go until 2 days after the wedding. I didn't think the site would recover from that.

The hardest part was to scale it economically. I have always been a big fan of SSD's, which are instrumental in scaling a site that doesn't have the resources to put data they need fast access to in RAM. For example, a site with more money might use redis to cache all the pics for each user (sorted, unique lists), plus all the tweets that point to a pic, but there is too much for me to do that in RAM without selling organs. Also, redis is not very memory efficient. But the advantage is that technologies like that are easy to use and easy to scale. If you have money.

The Twitter rule changes freak me out every day but I have not seen any specific moves that make me think they are after me. It is probably a matter of time, but then you need to think about what form that will take. Will they just cut off the Streaming API? That would be a big move. Will they remove pics from the streaming API? I doubt it. Will they make moves to single me out? That would be weird. Will they come after me with lawyers for caching tweets? I don't see that either. But, while I don't see anything specific, there are a lot of what ifs.

My advice is to use Twitter to get off the ground and then move away from Twitter altogether if at all humanly possible. That's the strategy they are forcing with their stupid rules, so maybe they will see the light at some point and rethink their strategy.