Probably depends on the the design of the frame. I have an older 1998 Cannondale CAAD3 with oversized tubing at the bottom bracket area, no problems. MY 2005 Lemond ($1300) had smaller diameter tubing and flexed more thn the Cannondale.

After 13000 miles, the frame went "snap crackle pop" on a seated climb!..I rode it at 220-245 lbs for nearly 3 years.