When ING Direct announced earlier this year that it was committed to growing online brokerage firm ShareBuilder Corp. despite news that it would have to eliminate 7,000 jobs, some credit unions wondered if they were getting mixed signals.

ShareBuilder had 125 credit union clients when it was acquired by ING in 2007. The relationships dropped to 50 by January as the online brokerage firm made adjustments with its co-branded partnerships. At the time, ShareBuilder said it had set a growth target of at least 20% for this year.

The decline in the availability of advisers may be the top driver of growth within the online brokerage space, said Isabel Schauerte, an analyst at research firm Celent and co-author of the report "Online Brokerages: Technology and the Customer Experience." Fewer people are attracted to sales-based financial services positions, and there is a lack of development and training of new advisers, she noted. Many advisers are retiring, especially with the recent decline in markets and the move to cash. Brokers who are making less than they have in many years are taking this opportunity to exit the business or to make severe cutbacks on the size of their book, she found.