What are the similarities between a dot-com bubble and a crypto bubble?

Both are similar,

Both had investors who invested into internet technology

Mindset of both the investors were similar in a lot of ways because the motive behind the investing in both cases was same, they were/are investing looking for a bright future ahead and biggest of all reason was/is to make money

So as long as people investing into something share similarities everything associated with them are same.

Saying Cryptocurrency market is a bubble is similar to saying stockmarket was a bubble prior to 2008 crises. When and Why Did the Stock Market Crash in 2008? (https://www.thebalance.com/stock-market-crash-of-2008-3305535)Amazon, Facebook and many other internet firms today are product of dotcom era so saying dotcom era was a flop is a blunder.

Coming to CryptoCurrency market today, ya the whole market today is overvalued because we can never have a firm today that is worth billions of dollars without a finished product but in case of CryptoCurrency market we are having coins worth billions of dollars marketcap with no finished product in market. So ya definitely oneday this market has to come down but the real invention and real blockchain world is going to start after that and on that day of fall only few coins will survive the storm. So no CryptoCurrency is definitely not a bubble neither was dotcom era this is what I think, I would say these market crashes are just some harsh means of making us realize what is really worth sustaining in the long run and paving way for the beginning of something really great and unthinkable.
So I would say it's just beginning of something great to come,

Invest responsibly in few chosen coins that have the potential to survive the crash and storm and everything odd that's going to come in the near future. Am so optimistic about this crash because someday the prices have to show the real valuation of a company and when the whole Crypcurrency market becomes mature, the investors gonna pullout money from the unworthy projects and invest them into some real projects like Ripple,Tron,Privacy coins etc..And when this happens the markets gonna trumble and many of these coins gonna fail on that day leading to a potential market crash but this day isn’t the day of bubble popping but this day would mark the beginning of Blockchain world and am sure the worlds gonna change after that day,as internet has changed the world after its emergence.

As Dominik Zynis, advisor to Wings - DAO Platform (http://Wings.ai), says with regard to Blockchain and the WWW:

“The World Wide Web democratized the content lifecycle (creation, distribution, rating, consumption). For example, we no longer get our news from two or three channels, instead, we get our news from friends and associates sharing on places like Twitter, Facebook and Snapchat. Likewise, Blockchain technology can democratize the money lifecycle; however, to do that Blockchain technology must enable and empower the unseen and unimportant.”

He goes on to say: “Just like companies like YouTube, Instagram, Snapchat and others capitalize on the long-tail of content creation empower cat owners to distribute cat videos, so too must Blockchain technology through projects like Counterparty creating PepeCash and BANCOR Network creating local coins enable the long-tail of coin creation.”

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Tipjar:
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Ripple address : rLdinLq5CJood9wdjY9ZCdgycK8KGevkUj
Litecoin address: LfqV2RSxvTD3podwfd4iEY1MfeDPMYspEm
Ether address: 0x547d0fa385dfd68c47c8ac50eff1026b09ba772e
Dash: XdtLYwtk6N54cFovy5W5DRhTyzzLqHQeiS
Paccoin : AfCw9VbAJYar9gxadjZ4PQfxAcHWsyyyCE
Cardano : DdzFFzCqrhseF3pZN8Gu27CpeUCBXj4ug6pjGtRkMdckPSgpVksdNhyaXSEnHBFvBhJGkPXPRUHVp1WMfyb2U2YQonx5woRESaSKbEHe
Tron : 0x04da7ef1735344ed0985a995792d1babe03541f2
Verge : D9brHaN8SPB86JY1xWfwmUJoiMopcvw3hT