I didn't think many people were still reading.
I looked one place for spoilers real quick and nothing major except this:
Episode 2.14: One Of Them
Airdate: February 15, 2006
01/28 - When Rousseau leads Sayid to a mysterious captive in the jungle, he becomes determined to find out if he is one of the "Others.'' Source: WCHS
01/03 - [This episode] is Sayid-centric with a flashback to Iraq. Sayid deals with a CIA agent (George Clooney type) named Inman. Source: SecretAgentMan at TWoP
and this was pretty interesting:
01/25 - Writer/Supervising producer Javier Grillo-Marxuach reveals (note that this is a summary of the spoilerish things he revealed): Eko facing off against the 'monster' is a big deal in terms of the series because he's the only person - next to Locke - who has seen the 'monster' and has lived to tell the tale! Only with Eko, it was a different kind of encounter. That is something that the fans can expect to see bear fruit in future episodes. It's a hugely important thing, but won't necessarily be revealed immediately. [...] What you're going to see with Eko is that he has his own destiny on the island, and of all the characters, he has the most direct connection to the island because of the Nigerian drug plane. That's going to pay off in different ways. It's not going to mean necessarily that we wind up giving you the history of the 'monster' as a result of its interaction with Eko, but it sends Eko in a direction where he has a destiny to fulfil on the island that's gonna pay off. [...] What happens in episode #11 with Mr. Friendly showing up again, making himself seen and making his laws of the island very clear to the characters, will ripple throughout the rest of the season in a very meaningful way. [...] You're going to begin to see a lot more of the Others, and see a lot more of what they're about and what they're doing. Source: The Official Lost Magazine, Issue 3, March/April 2006
I've never been good about solving these puzzles, but I wonder if Sayid could (possibly) be an Other from before (like his dealings with the CIA) or if something happened when he was with Danielle. Didn't she inject him with something?
ETA:

after having some caffeine and reading this again, I realize now Sayid is determined to find out if the captive is an Other, not if Sayid himself is an Other. Duh! It would have been much more interesting they way I thought it.