The author is comparing a disruptive innovator (Netscape) with incremental features (Yelp and Twitter). Netscape truly changed the world by making the Internet accessible to millions of new users, while Yelp created a Bay Area and NY centric yellow-pages -- useful, but hardly innovative.
A very good point about the disruptive innovator being compared to incremental changes. That being said, Yelp is in a much better position than Netscape was in terms of revenue generation ability/potential and ultimately that is what IPO's focus on.
Netscape the product was disruptive, but was it ever a great company?
The 2010 Tech IPOs would (provided they occur, which isn't quite a given) all be years in the making and coming from profitable companies with hundreds of millions in revenue. That's quite a change from the nineties tech boom.
Seems only Facebook has the potential for a Netscape-like IPO, and even then I don't think it'll be in 2010 nor that it would lead to a dot-com bubble (although if it does, I'll make sure to get in early)
Go ahead an put your (fake) money where your mouth is :)