Although there aren't many of "us" in this field, I haven't seen any obvious signs that would indicate any calculated effort to keep the population low.
I've worked in the IT industry for over a decade, performing duties from phone support to system administrator to system engineer. I've done a lot of government contracts and have worked for companies like Northrop Grumman (Fortune 500), , ManTech International ( and BAE Systems. )
The way those contract jobs work, a recruiter goes through all the resumes and tries to find people who the government will hire for the most money. In our little circles, we joke about how if resume comes across a guy's desk with a "black-sounding" name, it'll get tossed out. But seriously, sometimes I feel that with a name like Theodore and a somewhat recent graduation date, they may assume I'm young and white.
I really don't see a lot of African-Americans in IT, but I don't think you can pin that to one issue. I think it's a lot things. Education is a part of it. Some of it is cultural differences, segregating ourselves by choice and the younger generation not being interested in these opportunities.
It has been a good career, even though I've sometimes felt my minority status may have held me back occasionally. It's nothing concrete, just a general feeling or a little comment here or there. But hey, that could be my baggage. I grew up in the '60s, after all.
Diversity in Silicon Valley is opaque. A CNNMoney investigation aimed to uncover it, but we received data for only a handful of companies.