I used some CoinDesk data to look at 160 ICOs from 2014 until present day.
The dataset has 160 companies that cumulatively account for around $1.7bn raised.
(I tried to clean the data for duplicate ICO names, where the company had multiple funding rounds)
There are 28 different extensions represented in the list. The top 4 are:
TLD, CountUnique
COM, 55
IO, 34
ORG, 18
NET, 8
If we use these ICOs are a proxy for the crypto market overall, it does look like .IO are quite popular.
Take this with a pinch of salt, as crypto-dedicated content sites (news, blogs, forums etc) may have an entirely different composition of extensions.
The list of ICO titles/names is also incredibly diverse - and there isn't a consistent naming pattern. But no prizes for guessing some of the common words found: coin, project, network, chain, block, cash, etc.
Finally, I also began to look for patterns to correlate funding size to extension but I don't feel like there's any particular pattern of significance. The surprise for me was the use of .network as the fifth most popular extension. With 8 ICOs spanning $209m of funding, .network was the fourth highest funded TLD.
Bar chart below and link to data source
here