What (Sethbling and) I expected to happen was:
If a player's name is formatted by their team in the scoreboard system, it would be displayed formatted when command blocks use the /say command with @p/@a/@r.

What actually happened was:
As seen in Sethbling's livestream at 2:40:00, the /say command does not display players' team colors/prefixes/suffixes: it just displays their name without any formatting.

The name is formatted in player chat, overhead, in the player list, and on scoreboards - specifiers in the /say command seem to be the only exception.

Steps to reproduce:
1. Create a team with "/scoreboard teams add test"
2. Change its color with "/scoreboard teams option test color green"
3. Add yourself with "/scoreboard teams join test"
4. Say something in chat (don't use the /say command), and observe that your name is green.
5. "/say @p", and observe that your name is not green.

Potential issue:
While I feel this bug is an oversight due to how @p/@a/@r is substituted for actual player names (as far as I know), fixing it may require a special case (e.g. only apply to the /say command, and for any argument after the first one in the /tell command), as it would ordinarily prevent command blocks from working on players who are on teams.