I have a VPS I found on lowend box. $5/month for a 512MB OpenVZ. It's a pretty good deal, and it does what I need it to do; I have full control over it, I can give other people access to it, I can run any kind of website on it as long as I don't care too much about performance or uptime.
But there's no way I would run any service that was bringing in money on it. It basically has downtime every single month. Usually only for a few minutes at a time, and they tend to scrape by just barely exceeding 99.90%, but still. There also was one time when they emailed me saying there had been a power loss or some other reason that the rack my server was on went down, and I actually ended up having to go into the console to start my server back up and get everything working.
I've also found their support ... not particularly supportive.
Sure, Linode is 4x as expensive for the "same thing" (though to get Xen from my provider is only about 3x cheaper than Linode), but the amount of total money is negligible. $15/month. Maybe if I needed more resources it would be a difference of $100/month, but if I need a 4GB VPS for a service that's meant to make me money, that should still hopefully be trivial. For a service provider with much better uptime and support, that's a no-brainer.