i think the main difference between now and 1999 is that software really is eating the world. 1999 jumped the gun a little bit. but to me there is no upper limit on just how much work software will be able to do for us going forward, now that the infrastructure is in place to support such a transformation. i think there is a lot of hype, but unlike in 1999, when nobody was sure what the value of the internet actually was, it's based on a central fact: the world of the future will be operated by software.
i'm sure there will be booms and busts but i don't think they will be nearly as severe as in 1999.
Furthermore, I'd say the world of software has diversified greatly beyond what we had in 1999. Social media companies with no revenue may experience a bubble pop, but I don't see that being an issue for VCs, whose portfolio contains completely different kinds of tech companies like Uber or Liquid Robotics for example.
I think this is one of the best points. The environment is different.
Why are "apps" companies taking off? Because Google, Microsoft, and Apple are actively selling billions of phones to customers. These customers, in turn, fuel the app market. This is not a "bubble". These are consumers buying real products with real value, making companies real money. This isn't a "potential" type of deal, this is happening and fuels some of the biggest companies.
Why are companies like Google making money through advertising and why are other sites using Google's ad system to make a ton of cash too? Because there's a market for it. People visit the internet, they see ads, they click on them and buy. Products and money gets exchanged. Amazon is in on the deal too because, guess what? People buy products from their site.
Now, why is Snapchat and Pinterest so highly valued when they make 0 revenue (albeit Pinterest having tried the affiliate game for a short amount of time)? Because of the existing markets and companies that can profit on their products. Pinterest is already trying out revenue models, how? Affiliate programs where people click on pretty pictures of something or the other, buy the product and pinterest makes cash. Nothing magical about it. Snapchat will be harder to monetize but could "easily" be purchased and used as yet another product for a company to capitalize on and get someone trapped in their ecosystem. See facebook about instagram. Same deal.
I'm not as familiar with the dot-com bubble as others but seeing revenue happening because people are moving to more of an online world rather than an offline one makes sense. People buying products, purchasing subscriptions to entertainment, buying subscriptions to useful utilities (eg. dropbox) makes sense. Ad companies fueling online advertising to get people to buy shit or subscribe, makes sense. Companies that profit on having users and engaging those users while advertising for companies that sell products, makes sense.
i'm sure there will be booms and busts but i don't think they will be nearly as severe as in 1999.