Not to sound like a jerk but I really am surprised that these businesses are coming back to life. I tend to wonder what brings some businesses back to life, after all they failed don't most people like to throw insults and dance on the graves of failures? So anyway I know there are a couple other businesses that have risen from the dead recently which I can't remember (I'll add more as I come across them). So here are the ones that I can remember. The only reason I know Bolt is back again is only because they emailed me, otherwise I haven't heard any of the usual blogs (TechCrunch, Mashable) say a thing.
Nau
This company makes a lot of well designed apparel using environmentally friendly methods/materials. While their designs were great I always questioned their pricing. Perhaps now it'll be a bit different this time around. One other problem from before was the over-use of Flash for their website design, and unfortunately they are still over-using it on the new site. Seriously people stop with the Flash. I have always felt that Flash was great for promotional purposes and I still do. However, using it for your whole website is just crazy unless your website is some sort of elaborate Flash-based application (example: Pandora).
Bolt
Overall Bolt never really offered anything that amazed me much. Nothing really distinguishes it over other networking sites. Why does that matter? I'd say because there are already several good general-interest networking sites like MySpace and Facebook. I only get excited these days when I find a well done networking site that is focused on a niche that I care about.
Sharper Image
The brick-and-mortar stores annoyed me, but their website has actually been a regular resource for me to find things I'm searching for. If they stick with just the website this time around they should do fine but the stores were tacky. Now if only Brookstone would drop their retail act. (Oops nevermind Engadget is already reporting that they will live on as just a brand. Which is practically the worst possible thing they could do.)
Moviebeam - ADDED July 14, 2008
I was kind of happy when this company went under, mainly because it required purchasing another practically useless set-top-box. These things still use wires, ya know. I'd say the only set-top-box worth buying is either an Xbox or PS3, which are game consoles that double as many other things. What gets me though is that people are still trying to make money off boxes you plug into your TV. Talk about re-inventing the wheel, there's a box that already does everything it's called a computer. If more companies would integrate software like Splashtop, then I'd hear even more people agreeing with me.