I've now been through two races this year where I was riding solo and there where 2 or 3 teams with large numbers or riders. In both races breaks went up the road with representation by the big teams, and then the remaining teammates in the field went up to the front and blocked, creating congestion at the front and riding less then 20 miles per hour. Any time anyone went to the front to speed it up the big teams would shut it down. Any attempts to bridge where chased down too.
In the first race this tactic failed completely, even with the blocking the break cracked and we caught them at 1k to go. No one from the team that did all the blocking ended up on the podium.
In the second race two teams did a bunch of blocking. One of the riders ended up winning solo, but the other team missed the podium completely (I won the field sprint for second after chasing, like a mad man multiple times, so ha).
Here's the question then, is blocking a legit tactic? The answer - NO.
I've seen three teams try it this year and they're one for three. If a team adopts a negative tactic like blocking, they are putting all there bets on one scenario. If they aren't willing to commit to counter attacking and just hope their lone breakaway rider can stick it. They don't really have a good chance of winning. This past weekend was a good example of that. One team had two riders in the break. They both cracked and even though there wasn't much of an organized chase both riders from that team where caught.
Fast, positive racing with attacking, chasing and countering, is the best way to race. The weak riders get shelled, and the strong riders contest a safe finish. Simply put, if you can't ride fast, you don't belong on the front slowing the race down. Get out of the way, go home and do some intervals, and come back next year when you're fast enough to actually race and not be a sissy.