Stella Creasey, the BBC's head of audience research, said they only attracted an average of 3,000 phone downloads per mobisode.
"That's not many," added Ms Creasey. "It seems we have a long way to go to understanding this new space."
The Guardian has the grif.
Perhaps Skype can provide an answer.
One problem, said Iain Tweedale, the new media editor for BBC Wales, was that even though the BBC provided the mobisodes free, most users had to pay a charge to their phone operator of between £1.50 and £2 per Tardisode.
"The fact that there were 2.6 million downloads to PCs shows that there was an interest, so I think the problem with mobile was purely a commercial issue," said Mr Tweedale.
"The operators' tariff structures aren't flexible enough to allow for low-priced usage," he added.