I've seen this play out several times and figure an article on some basic strategy would be helpful to the masses.

Lets set up a hand:

The game is NL Holdem, Multi-table tournament. Blinds are currently 200 and 400, ante 25.

Stacks are as follows for key players:
Small Blind : 1150 (~3 BB)
Big Blind: 3820 (~9 BB)
UTG: 6659 (~17 BB)
Dealer: 12115 (~30 BB)

UTG is first to act and has [A][A]. UTG limps in for 400.
Table folds around to Dealer. Dealer limps in for 400.
SB call 200.
BB checks.
At this point the pot has 1825 in it. This isn't really relevant with the course of this hand or how it played out but is always a good number to know.

Flop comes [5][10][5]

Action on flop is as follows.
SB and BB both check.
UTG leads out minimum bet, 400.
Dealer calls 400.
SB fold, BB calls 400.
Action is now complete on flop and the pot stands at 3025.

Flop analysis
At this point in the hand the UTG has taken control of the pot. The player has 2 Aces in the hole and is in position against one player and out of position against the second. The dealer has not shown strength in this hand yet; However, the BB decided to see the flop for free and then decided to check-call. The flop has no flush or straight draws present. The BB could have a hand with the 5 in it, they may also be holding on to a [X][10]. It is unlikely the BB would remain in the hand out of position without a piece of this flop. A weak 10 is most likely at this point in the hand.

The Turn card is [7], making the 4 card flop, [5][10][5][7], and the action is as follows.
BB again checks.
UTG leads out 400 again.
Dealer calls 400.
BB check-raises all in for 2995 total.
UTG calls, Dealer folds.

A few things to consider in this hand as the UTG player after the BB pushed all-in are the pot currently stands at 6820 without the call, assuming the dealer folds (which we know will be the case), the UTG player has 2.6 to 1 pot odds. The UTG should be thinking about what the BB has that would constitute an all-in. The BB has not been aggressive in this hand up until now. It is possible they have a 5 in there hand, or possibly even [7][7]. A 10 is also possible. The Dealer has also cold called everything, they could be holding onto strength as well. They may have limped in preflop with an [A][5] or maybe even [4][5] or [5][6] suited. At this point the UTG should seriously consider folding. The BB is not pushing here on a bluff, the best case scenario it they have a [10] in their hand. The Dealer is yet to act and could be holding onto a [5] if the BB does not have it already.

The hand plays out with the UTG calling the all-in and the Dealer folding the second bet.

The hands are revealed and the BB does in fact have a [5], their hand is: [5][4].

The river card is a blank and the BB wins a large pot.


Post Hand Analysis
Very often many players decide to limp in with large hands such as [A][A] from early position in hopes of someone else opening the pot. The downside to this play is if no one else opens the pot and the flop is seen with the blinds and additional players. At this point the value of 2 Aces greatly diminishes. As is evidence in the above hand the UTG player overplayed his/her Aces and lost a large pot. If the UTG had decided to open the pot with a min-raise the likelihood of the blinds folding are high. Neither player in the blinds had a stack size of over 10 BB and committing additional chips to the pot preflop would only decrease their stack size more if they didn't hit their miracle flop. While limping with a strong hand like this isn't a bad play, it should be noted that aggressive play post flop loses a large amount of value when both blinds and a player in position remain in the pot.

As a side note to this analysis, I want to thank the players involved in this hand. I have decided not to post the screenames of those involved. This hand struck me as being an interesting one, and one that I see far to often on PO. I understand that pointing out flaws is -EV for players that can win on here, but as a poker forum it is also important to spread the wealth and help other players out. Good luck on the felt.