Another tech bubble?

In the late 90s, things went a little crazy. We had websites popping up here, there and everywhere that allowed us to do lots of exciting things, mostly for free. It turned out that this kind of business model wasn't generally very successful so most of these sites went bust. At the time, being an IT professional was pretty good, since the job market was red hot. Then suddenly in 2000, it all went tits up. So here we are in 2006 and the job market is moving very quickly upwards,lots of new websites are popping up doing lots of exciting things, mostly for free, many with a business model that seems to entail nothing more than ad revenue, or value added services. So is this another bubble or is this different? It seems to me the key here is the growing online ad business which is doing very well at the moment. It seems slightly crazy to me that I can get paid $1.50 just because someone clicks on a link on my site (and the advertiser is paying even more). If that stream of revenue stops or severely reduces, a lot of these new web businesses might start having problems I reckon.