Two helpings of Facebook shares apparently weren't enough.  Russian investment firm Digital Sky Technologies has gone back to the well for a third time, spending perhaps $100 million to buy still more shares in the social networking company.

Digital Sky first demonstrated its appetite for Facebook shares back in May, when it spent about $200 million acquiring a small stake.  The firm next invested another $100 million in July, which netted it a total stake of 3.5 percent.

This latest push isn't likely to represent any sort of takeover effort, then, as Reuters reports that Digital Sky is still willing to value Facebook at $6.5 billion.  Only one source told Reuters that Digital Sky would invest "up to" $100 million this time around, as well, so there might be less money changing hands. 

Nonetheless, a Facebook shareholder also told Alexei Oreskovic, "Their appetite with me is: 'whatever you have, we'll take it,'" and that combined with the steady valuation demonstrates a fair amount of confidence in the company.

The investment is also interesting given that word of it leaked even as the Dow and the Nasdaq are already both down by more than 0.55 percent this morning.