It's happened from Coinbase and Multibit.  Here is the FAQ for the Multibit one: https://multibit.org/en/help/v0.5/help_support_sentBitcoinFromMultibitButTheyAreStuck.html


Here is Multibit reasons for a transactions not being broadcast:

There are various reasons why a peer does not relay a transaction. In a rough order of frequency they are:

    There are lots of tiny inputs (under 5432 satoshis) in your wallet and the transaction fires the anti-spam rules.
    The fee is too small and the peer chooses not to relay it.
    The transaction is a double spend. Doubles spends aren't relayed through the network.
    Some other reason - this is not a definitive list.


Mine fit into option 4: "Some other reason - this is not a definitive list"


So basically NO reason???

This has happened to me 3 times now! I get a 15 min invoice from Bitpay and I immediately  send a payment from Coinbase or Multibit, but the transactions never shows on the blockchain and the invoice expires. I search the transaction hash on the blockchain.info and I get this error "Sorry we could not find any blocks or transactions matching this hash". I then send a second payment from the wallet and the transactions show instantly on the blockchain!

Why is this is unreliable? Why do some transactions show immediately on the blockchain and other do not? It is VERY frustrating!

Funny I sent another payment out from Coinbase and it showed up immediately in the blockchain and the one to Bitpay still is not showing. I wonder if they don't want to send transactions to their competitor . 

This has happened to me 3 times now!  I get a Bitpay invoice with a 15 min timer, I send a payment immediately, but the transaction never shows up in the blockchain and the invoice expires.  And the coins have left my wallet! It's happened paying from Multibit AND Coinbase! I hate this! Sometimes it's instantaneous, but other times it randomly does this crap!  Is this a flaw with the Bitcoin protocol? Why isn't it more reliable??? So fing frustrating!

Woah this one has margin and lending options... Really advanced stuffs!

Hello,

 I want to do a little bit of day trading with some Bitcoin.

What site is best?

Btc-e
CoinMKT
Mt Gox
Other?

I will only be trading to try to increase my coin holding so I do not expect to need to withdraw or deposit cash. Only deposit and withdraw Bitcoin only.

Which of these sites is the most user friendly, lowest fees and has the best costumer service?

I'm in the USA if that makes a difference.

Enter in your total BTC amount in to this search and then post your rank! Let's see how we all compare.

http://btc.ondn.net/search

Shut up! $45,000 is the end game!!!!!!!!    No stop till we get there!

Glad to be onboard!