Nothing funky about TB being in the top...and Keith Richard made a very astute observation.
If you're talking about betting on one team, the key to making money on MLB moneylines is fading or backing a team whose play turns out to be the inverse of what's expected. Every year there are teams that do far better than expected (this year: Texas, Cincy, Tampa, Detroit...not coincidentally, the top money makers) and teams that fare worse than expected (Seattle, Arizona, KC).
The key is not to bet the best teams who are expected to win...the odds account for that. I suspect that putting $100 down on the Yankees every game from here on out will net you a loss. But it takes the oddsmakers time to adjust the lines in accordance with reality, as the public's perception of the 'better' teams takes a long, long time to change...and this is true in every sport.
Eventually though, the linesmakers will catch up. The lines on TB, Texas and others will adjust to coincide with the new reality; that these are halfway decent teams. To beat the books, you've gotta pick a team that has *NOT* performed well up to this point, and isn't expected to turn it around...or the converse, a team that has done well and will fizzle. Bet on or against those respective teams before the new reality sets in, and you should make nice $$.
If I had to pick one team that I think will play much much better ball from here on out, it would be Pittsburgh. This is actually the ideal type of team to bet on...chock full of above average hitters and pitchers who are largely unknown out of metro Pittsburgh. But take a look at the stats, and you'll see what I mean...this team has a bundle of talent, but haven't started stringing together substantial numbers of wins yet. They will, and they'll do it before the linesmakers adjust. Pitt should be a winner from here on out.
Another team that's done surprisingly well this year is Milwaukee, but unlike Pittsburgh, I don't know if they have the pitching to sustain a prolonged winning season.
Montreal's got some of their hitters back, and should play a bit better than their woeful record up to this point would indicate, though that ain't saying much.
Great team to fade? Toronto. They are absolutely abysmal. Without Wells and Delgado in the lineup, they field a triple-A team. Their offense is a joke.
Another team that might be worth fading is Atlanta. 10 years of winning the division will place you in very high esteem among bettors, but these ain't your big brother's Braves. Chipper and Andruw are having horrific season, and the rest of the lineup (save Furcal and Giles) plays like a who's who among the confectioneers at the Fulton County Fair. I haven't really been tracking their lines, but if it hasn't already started to adjust, one can't expect them to be worth whatever price they're asking.
The Rockies, with Walker and Payton back, should muster a few more wins now. They've been golden as a road under team up to now; that may change.
The Padres are for real, and should compete...though I think they need another arm. The lineup is quite nice though.
As for a team that might decline before season's end, nobody really comes to mind. Like I said, I doubt Milwaukee will keep it going, but I don't think they've gotten the respect from the linesmakers that a +.500 team should get anyway, so there's not much value in shading them. St. Louis' staff is comprised of journeymen having career years, but their lineup is so awesome it's hard to feel comfy betting against them no matter who's on the hill. Same with Anaheim, if they can keep healthy.
Sorry for the longwinded post...I didn't check any stats, just basing all this analysis on my day to day baseball observations. The point, and the key, is to spot or anticipate trends and pounce on them before the public catches wind of them.
And again, my strongest feeling is that Pittsburgh should be the next Tb...surprising a lot of teams through the rest of the year.