The largest belong to exchanges  supposedly in safe custody for...

The largest belong to exchanges  supposedly in safe custody for clients . This is crazy when you consider that BItcoin was created as a decentralised asset and then some individuals went  and centralised it . It was created as a decentralised asset to remove the  so called trusted  middle agent who have a long history of not being trustable. Why was it centralised ?

     1. convenience

     2. Those individuals saw a decentralised  asset and said I can get in there and clip a ticket each time someone does a transaction.

1		1	3D2oetdNuZUqQHPJmcMDDHYoqkyNVsFk9r3-of-6 wallet: Bitfinex-coldwallet	138,661 BTC (1,457,892 USD)	0.7946%	2017-01-05 23:34:15	2018-12-24 02:06:43	5594	2017-01-06 21:29:06	2018-10-23 00:45:07	4541
2	2	352USv8Cih1Bq81XnzB2C9VLMQBh55Y4uV wallet: Binance-coldwallet	109,232 BTC ($426,542,170 USD)	0.6259%	2018-11-20 21:14:20	2018-12-11 01:00:27	11
3	3	3Cbq7aT1tY8kMxWLbitaG7yT6bPbKChq643-of-5 wallet: Huobi-wallet	108,135 BTC ($422,255,851 USD)	0.6196%	2017-09-09 02:41:05	2018-12-25 13:49:38	224	2017-09-09 21:18:35	2018-04-25 17:53:53	9
4	4	3Nxwenay9Z8Lc9JBiywExpnEFiLp6Afp8v3-of-5 wallet: Bitstamp-coldwallet	107,848 BTC ($421,137,599 USD)	0.6180%	2015-10-17 01:43:06	2018-12-17 01:54:11	218	2015-10-29 21:44:26	2018-08-16 04:16:05	60
5	5	16rCmCmbuWDhPjWTrpQGaU3EPdZF7MTdUk wallet: Bittrex-coldwallet	107,203 BTC ($418,618,120 USD)	0.6143%	2016-02-28 05:00:09	2018-12-19 10:19:13	185	2016-11-17 07:50:07	2018-07-05 03:31:23	67

The amount held by exchanges is almost certainly greater than  this  as  for instance  coinbase recently broke up its  large wallet into five separate segwit compliant wallets .A wise security precaution as  each wallet would have to be hacked  but still not as secure as owning your own keys .

The largest individual holders  of coin probably spread across multiple wallets are believed to include  a number of the original cypherpunks  plus nakomotos . Sadly missing is  the late Hal Finney the first man to recieve a bitcoin transaction  his coin was used to pay for  his treatment  for Multiple Sclerosis. The fact  that nakamotos wallet has not been accessed for the same purpose or by Finneys widow makes it unlikely that he was nakamoto . He would surely have given the keys to his wife while she was nursing him  ( see banking on bitcoin movie).

                                                                                                SO TO ANSWER YOUR QUESTION

My opinion is that in the stages of adoption  there will be concentration in individuals and then diffusion . Can those individuals act in a rogue manner?  they already are through the standard whale trick of buying on OTC  and then selling a proportion  on exchanges  to push the price down so they can buy again.

As far as that concentration being with criminals  I have posted many times on how law enforcement can  now trace bitcoin transactions with a clarity that they can not with fiat. However as long as the media ( read newscorp in particular here) keep putting out the incorrect information  that they cannot be traced law enforcement clean up rate will be enhanced