Overstock is in the business of reselling items, and I don't believe they're accumulating cryptocurrency. There's an advantage to using it for them, but I can't imagine they're just going to sit on it and not convert it to USD. They pay their employees and all their bills and everything else in fiat. Make sense?
"At present we do not accept bitcoin payments directly, but use a third party vendor to accept bitcoin payments on our behalf. That third party vendor then immediately converts the bitcoin payments into US dollars so that we receive payment for the product sold at the sales price in US dollars."
Overstock uses Coinbase as their payment processor. Both Coinbase and BitPay offer their customers the option to retain a percentage of coins in the form of BTC.
Very few businesses that use them choose to exercise this option. Overstock converts the majority of their received coins to USD but unlike most other businesses that claim to accept BTC, it also keeps a small percentage of these coins as BTC:
US retail giant Overstock lost $117,000 on its investments in cryptocurrencies during the first quarter of 2015, according to the company's latest quarterly earnings report.
Overstock listed its cryptocurrency holdings as valued at $233,000, down from $340,000 on 31st December.
Long one of the largest merchants in the digital currencies space, Overstock had previously indicated that it was holding as much as 10% of its proceeds from such sales in bitcoin.
Link:
http://www.coindesk.com/overstock-reports-over-100k-in-bitcoin-losses-for-q1-2015/As for what altcoins, they might have invested in - I don't know the answer to that. However, Overstock has expressed interest in asset exchanges in the past which sort of gives an indication of where they might have poured their money into:
Overstock.com and its swashbuckling CEO, Patrick Byrne, are hoping to create a new kind of corporate stock based on the computer software that drives bitcoin, aiming to overhaul the stock market in much the same way that bitcoin overhauled how we store and exchange money.
On Tuesday afternoon, Overstock - one of the world’s largest online retailers, with $1.3 billion a year in sales - unveiled a webpage that explores how a public company could issue a "cryptosecurity" to potential investors. In an echo of the bitcoin digital currency, this would be a stock that’s controlled by cryptographic algorithms running across a network of computers owned by people and companies spread across the globe.
This spring, Byrne indicated he would let others build such a system, but the 51-year-old - a three-time cancer survivor - has a way of changing the course of his company as the mood strikes him. Asked if the new wiki showed that Overstock intended to issue a crytosecurity, he stopped short of saying so. "Before we decide if we want to issue a cryptosecurity, we want to figure out if it’s possible," he tells us. But Overstock has already held extensive discussions with the founders of a project called Counterparty, which offers software that could help drive such a cryptosecurity, and if he decides this kind of thing is possible, he intends to "open source" a blueprint of his plan, so that any other company can make use of it.
His efforts are part of a much larger movement that seeks to remake the stock market in the image of bitcoin. Several projects - including NXT, Mastercoin, and Bitshares - are working on software that’s similar to the tools offered by Counterparty, and all are mentioned in the Overstock outline. What’s more, others are looking to apply the bitcoin way to additional financial instruments, including derivatives, and some software developers are even using the idea of bitcoin’s public ledger - known as the "blockchain" - to remake tasks beyond the financial world, including secure online messaging.
Link:
http://www.wired.com/2014/07/overstock-and-cryptocurrency/Their wiki page on how to issue a cryptosecurity mentions the above platforms as well as a few others:
http://www.o.info/How_to_issue_a_cryptosecurity