The San Francisco 49ers know that they're not exactly the strongest 3-1 team--beating Seattle doesn't mean much, the Cincinnati game was tough to watch, and Philadelphia clearly looks like a flawed team. Nonetheless, they're 3-1,, so things have to be looking up. The Tampa Bay Buccaneers are in a similar position; they have a decent win over Atlanta, but they also have wins against 0-4 Minnesota and 0-4 Indianapolis. Far from the ideal resume to pump people up.
It's why the 49ers being 2.5 point favorites over the Bucs makes perfect sense. Neither team really is all that much different from the other. Even if Tampa is travelling cross-country for this one, Candlestick Park hasn't exactly been the most intimidating place to play as of late (outside of the parking lot and in the stadium, that is).
Harbaugh seems to have San Francisco turned around and getting things going though, so that line might move up a tad as the week goes by and people start hopping on the 49ers bandwagon (like they do every year).