"In 1981, the top ten technology companies represented 95% of the global IT market cap. Today, that share has fallen to 26% and the ratio continues to fall."
Microsoft, IBM, DEC, HP, and so on were once titans. Apple, Google, and Facebook may be titans now, but they capture less of the overall value in the industry than the old top players did. More of it is captured by a larger array of smaller companies, which is a fundamentally positive thing, IMHO.
The graph and opening quote are from an interesting and detailed post by Tomasz Tungunz.