I would say recession is kind of here, and coming (but def not depression, technically speaking the economy is going through depression, when it has been in recession for a couple of years and not coming out). but in terms of should you wait for it to go away, I really don't think so. If you have an idea then you should def implement it now, otherwise it will be too late for it. But you have to realize that if in case there will be a recession, then finding jobs might not be as easy either. So if you don't think you can live and sustain the startup life for a while, then you should be careful quiting your job.

Also, there is a lot of talks of online advertising revenues going down, and this might even damage companies like Google a lot. But if you feel like you have a product that would attract many eye balls then you should implement it without worrying too much about online ads, and also you might be able to either find a business model for it that doesn't solely depend on ads or find other interesting exit options for yourself,.

In terms of venture capital, it all depends on how much money your project needs. As many of the "web 2.0" companies don't require much capital to start, I wouldn't think it will dry up, but if more and more of them fail to eventually generate revenue, I would assume the VCs will get more selective. But since the capital needed is much smaller than the dot-com era I would hardly think that vc's will dry up. Of course that is IMHO.