Someone asked me if it's necessary to buy a Mac mini to run Lobster.

My answer is:
Absolutely not necessary.
First of all, Lobster isn't as practical as you might think; it's more like a fun toy. Putting it in a Mac mini or on a server makes no difference.
Your programming needs can be met by running Codex on your own computer. At worst, install a dual system; setting up Linux for programming is definitely enough.
If you want to experience Lobster, you can easily rent a server for less than $5 a month—safe and reliable. (Street哥 bought a server himself; even he, with all his money, didn't specifically buy a Mac mini, so there's no need for everyone to spend money chasing this trend).)
When do I recommend you buy?
When you actually have a need. I bought mine last September. I bought it because I could use Xcode on the Mac mini to compile Apple system apps, and the Mac mini is indeed awesome. With an HDMI spoof port, you can take it out, use your iPad as a screen—very cool. Just like a P4.
So, to summarize, if you truly have a need and plan to develop iOS apps in the future, then buy one.
If you're just trying to follow the trend and play with Lobster, definitely don't buy it. Rent a server instead. Lobster is just an intermediate product; renting a server to play around is enough. This thing isn't as fun as you think, and buying it just to gather dust isn't worth it.